diff --git a/speechx/speechx/asr/nnet/u2_nnet.cc b/speechx/speechx/asr/nnet/u2_nnet.cc
index e3277a38..0795c836 100644
--- a/speechx/speechx/asr/nnet/u2_nnet.cc
+++ b/speechx/speechx/asr/nnet/u2_nnet.cc
@@ -118,27 +118,38 @@ U2Nnet::U2Nnet(const ModelOptions& opts) : opts_(opts) {
 // shallow copy
 U2Nnet::U2Nnet(const U2Nnet& other) {
     // copy meta
-    right_context_ = other.right_context_;
-    subsampling_rate_ = other.subsampling_rate_;
-    sos_ = other.sos_;
-    eos_ = other.eos_;
-    is_bidecoder_ = other.is_bidecoder_;
     chunk_size_ = other.chunk_size_;
     num_left_chunks_ = other.num_left_chunks_;
-
-    forward_encoder_chunk_ = other.forward_encoder_chunk_;
-    forward_attention_decoder_ = other.forward_attention_decoder_;
-    ctc_activation_ = other.ctc_activation_;
-
     offset_ = other.offset_;
 
     // copy model ptr
-    model_ = other.model_;
+    model_ = other.model_->Clone();
+    ctc_activation_ = model_->Function("ctc_activation");
+    subsampling_rate_ = model_->Attribute<int>("subsampling_rate");
+    right_context_ = model_->Attribute<int>("right_context");
+    sos_ = model_->Attribute<int>("sos_symbol");
+    eos_ = model_->Attribute<int>("eos_symbol");
+    is_bidecoder_ = model_->Attribute<int>("is_bidirectional_decoder");
+
+    forward_encoder_chunk_ = model_->Function("forward_encoder_chunk");
+    forward_attention_decoder_ = model_->Function("forward_attention_decoder");
+    ctc_activation_ = model_->Function("ctc_activation");
+    CHECK(forward_encoder_chunk_.IsValid());
+    CHECK(forward_attention_decoder_.IsValid());
+    CHECK(ctc_activation_.IsValid());
+
+    LOG(INFO) << "Paddle Model Info: ";
+    LOG(INFO) << "\tsubsampling_rate " << subsampling_rate_;
+    LOG(INFO) << "\tright context " << right_context_;
+    LOG(INFO) << "\tsos " << sos_;
+    LOG(INFO) << "\teos " << eos_;
+    LOG(INFO) << "\tis bidecoder " << is_bidecoder_ << std::endl;
+
 
     // ignore inner states
 }
 
-std::shared_ptr<NnetBase> U2Nnet::Copy() const {
+std::shared_ptr<NnetBase> U2Nnet::Clone() const {
     auto asr_model = std::make_shared<U2Nnet>(*this);
     // reset inner state for new decoding
     asr_model->Reset();
diff --git a/speechx/speechx/asr/nnet/u2_nnet.h b/speechx/speechx/asr/nnet/u2_nnet.h
index 127d84db..35a15707 100644
--- a/speechx/speechx/asr/nnet/u2_nnet.h
+++ b/speechx/speechx/asr/nnet/u2_nnet.h
@@ -42,7 +42,7 @@ class U2NnetBase : public NnetBase {
         num_left_chunks_ = num_left_chunks;
     }
 
-    virtual std::shared_ptr<NnetBase> Copy() const = 0;
+    virtual std::shared_ptr<NnetBase> Clone() const = 0;
 
   protected:
     virtual void ForwardEncoderChunkImpl(
@@ -91,7 +91,7 @@ class U2Nnet : public U2NnetBase {
 
     std::shared_ptr<paddle::jit::Layer> model() const { return model_; }
 
-    std::shared_ptr<NnetBase> Copy() const override;
+    std::shared_ptr<NnetBase> Clone() const override;
 
     void ForwardEncoderChunkImpl(
         const std::vector<kaldi::BaseFloat>& chunk_feats,
diff --git a/speechx/speechx/asr/recognizer/CMakeLists.txt b/speechx/speechx/asr/recognizer/CMakeLists.txt
index 8f9117e4..f28c5fea 100644
--- a/speechx/speechx/asr/recognizer/CMakeLists.txt
+++ b/speechx/speechx/asr/recognizer/CMakeLists.txt
@@ -10,6 +10,7 @@ target_link_libraries(recognizer PUBLIC decoder)
 set(TEST_BINS 
   u2_recognizer_main
   u2_recognizer_thread_main
+  u2_recognizer_batch_main
 )
 
 foreach(bin_name IN LISTS TEST_BINS)
diff --git a/speechx/speechx/asr/recognizer/u2_recognizer.cc b/speechx/speechx/asr/recognizer/u2_recognizer.cc
index 0c5a8941..30595d79 100644
--- a/speechx/speechx/asr/recognizer/u2_recognizer.cc
+++ b/speechx/speechx/asr/recognizer/u2_recognizer.cc
@@ -43,12 +43,34 @@ U2Recognizer::U2Recognizer(const U2RecognizerResource& resource)
     input_finished_ = false;
     num_frames_ = 0;
     result_.clear();
+}
+
+U2Recognizer::U2Recognizer(const U2RecognizerResource& resource,
+                           std::shared_ptr<NnetBase> nnet)
+    : opts_(resource) {
+    BaseFloat am_scale = resource.acoustic_scale;
+    const FeaturePipelineOptions& feature_opts = resource.feature_pipeline_opts;
+    std::shared_ptr<FeaturePipeline> feature_pipeline =
+        std::make_shared<FeaturePipeline>(feature_opts);
+    nnet_producer_.reset(new NnetProducer(nnet, feature_pipeline));
+    decodable_.reset(new Decodable(nnet_producer_, am_scale));
+
+    CHECK_NE(resource.vocab_path, "");
+    decoder_.reset(new CTCPrefixBeamSearch(
+        resource.vocab_path, resource.decoder_opts.ctc_prefix_search_opts));
+
+    unit_table_ = decoder_->VocabTable();
+    symbol_table_ = unit_table_;
 
+    global_frame_offset_ = 0;
+    input_finished_ = false;
+    num_frames_ = 0;
+    result_.clear();
 }
 
 U2Recognizer::~U2Recognizer() {
-   SetInputFinished();    
-   WaitDecodeFinished();
+    SetInputFinished();
+    WaitDecodeFinished();
 }
 
 void U2Recognizer::WaitDecodeFinished() {
@@ -97,8 +119,8 @@ void U2Recognizer::RunDecoderSearchInternal() {
 void U2Recognizer::Accept(const vector<BaseFloat>& waves) {
     kaldi::Timer timer;
     nnet_producer_->Accept(waves);
-    VLOG(1) << "feed waves cost: " << timer.Elapsed() << " sec. " << waves.size()
-            << " samples.";
+    VLOG(1) << "feed waves cost: " << timer.Elapsed() << " sec. "
+            << waves.size() << " samples.";
 }
 
 void U2Recognizer::Decode() {
diff --git a/speechx/speechx/asr/recognizer/u2_recognizer.h b/speechx/speechx/asr/recognizer/u2_recognizer.h
index 57f2c9c5..5d628e3a 100644
--- a/speechx/speechx/asr/recognizer/u2_recognizer.h
+++ b/speechx/speechx/asr/recognizer/u2_recognizer.h
@@ -112,6 +112,8 @@ struct U2RecognizerResource {
 class U2Recognizer {
   public:
     explicit U2Recognizer(const U2RecognizerResource& resouce);
+    explicit U2Recognizer(const U2RecognizerResource& resource,
+                         std::shared_ptr<NnetBase> nnet);
     ~U2Recognizer();
     void InitDecoder();
     void ResetContinuousDecoding();
@@ -143,7 +145,7 @@ class U2Recognizer {
     void AttentionRescoring();
 
   private:
-    static void RunDecoderSearch(U2Recognizer *me);
+    static void RunDecoderSearch(U2Recognizer* me);
     void RunDecoderSearchInternal();
     void UpdateResult(bool finish = false);
 
diff --git a/speechx/speechx/asr/recognizer/u2_recognizer_batch_main.cc b/speechx/speechx/asr/recognizer/u2_recognizer_batch_main.cc
new file mode 100644
index 00000000..709e5aa6
--- /dev/null
+++ b/speechx/speechx/asr/recognizer/u2_recognizer_batch_main.cc
@@ -0,0 +1,185 @@
+// Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "recognizer/u2_recognizer.h"
+#include "common/base/thread_pool.h"
+#include "common/utils/file_utils.h"
+#include "common/utils/strings.h"
+#include "decoder/param.h"
+#include "frontend/wave-reader.h"
+#include "kaldi/util/table-types.h"
+#include "nnet/u2_nnet.h"
+
+DEFINE_string(wav_rspecifier, "", "test feature rspecifier");
+DEFINE_string(result_wspecifier, "", "test result wspecifier");
+DEFINE_double(streaming_chunk, 0.36, "streaming feature chunk size");
+DEFINE_int32(sample_rate, 16000, "sample rate");
+DEFINE_int32(njob, 3, "njob");
+
+using std::string;
+using std::vector;
+
+void SplitUtt(string wavlist_file,
+              vector<vector<string>>* uttlists,
+              vector<vector<string>>* wavlists,
+              int njob) {
+    vector<string> wavlist;
+    wavlists->resize(njob);
+    uttlists->resize(njob);
+    ppspeech::ReadFileToVector(wavlist_file, &wavlist);
+    for (size_t idx = 0; idx < wavlist.size(); ++idx) {
+        string utt_str = wavlist[idx];
+        vector<string> utt_wav = ppspeech::StrSplit(utt_str, " \t");
+        LOG(INFO) << utt_wav[0];
+        CHECK_EQ(utt_wav.size(), size_t(2));
+        uttlists->at(idx % njob).push_back(utt_wav[0]);
+        wavlists->at(idx % njob).push_back(utt_wav[1]);
+    }
+}
+
+void recognizer_func(const ppspeech::U2RecognizerResource& resource,
+                     std::shared_ptr<ppspeech::NnetBase> nnet,
+                     std::vector<string> wavlist,
+                     std::vector<string> uttlist,
+                     std::vector<string>* results) {
+    int32 num_done = 0, num_err = 0;
+    double tot_wav_duration = 0.0;
+    double tot_attention_rescore_time = 0.0;
+    double tot_decode_time = 0.0;
+    int chunk_sample_size = FLAGS_streaming_chunk * FLAGS_sample_rate;
+    if (wavlist.empty()) return;
+
+    std::shared_ptr<ppspeech::U2Recognizer> recognizer_ptr =
+        std::make_shared<ppspeech::U2Recognizer>(resource, nnet);
+
+    results->reserve(wavlist.size());
+    for (size_t idx = 0; idx < wavlist.size(); ++idx) {
+        std::string utt = uttlist[idx];
+        std::string wav_file = wavlist[idx];
+        std::ifstream infile;
+        infile.open(wav_file, std::ifstream::in);
+        kaldi::WaveData wave_data;
+        wave_data.Read(infile);
+        recognizer_ptr->InitDecoder();
+        LOG(INFO) << "utt: " << utt;
+        LOG(INFO) << "wav dur: " << wave_data.Duration() << " sec.";
+        double dur = wave_data.Duration();
+        tot_wav_duration += dur;
+
+        int32 this_channel = 0;
+        kaldi::SubVector<kaldi::BaseFloat> waveform(wave_data.Data(),
+                                                    this_channel);
+        int tot_samples = waveform.Dim();
+        LOG(INFO) << "wav len (sample): " << tot_samples;
+
+        int sample_offset = 0;
+        kaldi::Timer local_timer;
+
+        while (sample_offset < tot_samples) {
+            int cur_chunk_size =
+                std::min(chunk_sample_size, tot_samples - sample_offset);
+
+            std::vector<kaldi::BaseFloat> wav_chunk(cur_chunk_size);
+            for (int i = 0; i < cur_chunk_size; ++i) {
+                wav_chunk[i] = waveform(sample_offset + i);
+            }
+
+            recognizer_ptr->Accept(wav_chunk);
+            if (cur_chunk_size < chunk_sample_size) {
+                recognizer_ptr->SetInputFinished();
+            }
+
+            // no overlap
+            sample_offset += cur_chunk_size;
+        }
+        CHECK(sample_offset == tot_samples);
+        recognizer_ptr->WaitDecodeFinished();
+
+        kaldi::Timer timer;
+        recognizer_ptr->AttentionRescoring();
+        tot_attention_rescore_time += timer.Elapsed();
+
+        std::string result = recognizer_ptr->GetFinalResult();
+        if (result.empty()) {
+            // the TokenWriter can not write empty string.
+            ++num_err;
+            LOG(INFO) << " the result of " << utt << " is empty";
+            result = " ";
+        }
+
+        tot_decode_time += local_timer.Elapsed();
+        LOG(INFO) << utt << " " << result;
+        LOG(INFO) << " RTF: " << local_timer.Elapsed() / dur << " dur: " << dur
+                  << " cost: " << local_timer.Elapsed();
+
+        results->push_back(result);
+        ++num_done;
+    }
+    recognizer_ptr->WaitFinished();
+    LOG(INFO) << "Done " << num_done << " out of " << (num_err + num_done);
+    LOG(INFO) << "total wav duration is: " << tot_wav_duration << " sec";
+    LOG(INFO) << "total decode cost:" << tot_decode_time << " sec";
+    LOG(INFO) << "total rescore cost:" << tot_attention_rescore_time << " sec";
+    LOG(INFO) << "RTF is: " << tot_decode_time / tot_wav_duration;
+}
+
+int main(int argc, char* argv[]) {
+    gflags::SetUsageMessage("Usage:");
+    gflags::ParseCommandLineFlags(&argc, &argv, false);
+    google::InitGoogleLogging(argv[0]);
+    google::InstallFailureSignalHandler();
+    FLAGS_logtostderr = 1;
+
+    int sample_rate = FLAGS_sample_rate;
+    float streaming_chunk = FLAGS_streaming_chunk;
+    int chunk_sample_size = streaming_chunk * sample_rate;
+    kaldi::TokenWriter result_writer(FLAGS_result_wspecifier);
+    int njob = FLAGS_njob;
+    LOG(INFO) << "sr: " << sample_rate;
+    LOG(INFO) << "chunk size (s): " << streaming_chunk;
+    LOG(INFO) << "chunk size (sample): " << chunk_sample_size;
+
+    ppspeech::U2RecognizerResource resource =
+        ppspeech::U2RecognizerResource::InitFromFlags();
+    ThreadPool threadpool(njob);
+    vector<vector<string>> wavlist;
+    vector<vector<string>> uttlist;
+    vector<vector<string>> resultlist(njob);
+    vector<std::future<void>> futurelist;
+    std::shared_ptr<ppspeech::U2Nnet> nnet(
+        new ppspeech::U2Nnet(resource.model_opts));
+    SplitUtt(FLAGS_wav_rspecifier, &uttlist, &wavlist, njob);
+    for (size_t i = 0; i < njob; ++i) {
+        std::future<void> f = threadpool.enqueue(recognizer_func,
+                                                 resource,
+                                                 nnet->Clone(),
+                                                 wavlist[i],
+                                                 uttlist[i],
+                                                 &resultlist[i]);
+        futurelist.push_back(std::move(f));
+    }
+
+    for (size_t i = 0; i < njob; ++i) {
+        futurelist[i].get();
+    }
+
+    for (size_t idx = 0; idx < njob; ++idx) {
+        for (size_t utt_idx = 0; utt_idx < uttlist[idx].size(); ++utt_idx) {
+            string utt = uttlist[idx][utt_idx];
+            string result = resultlist[idx][utt_idx];
+            result_writer.Write(utt, result);
+        }
+    }
+    return 0;
+}
diff --git a/speechx/speechx/common/base/common.h b/speechx/speechx/common/base/common.h
index 2a066ee6..06fcd9fd 100644
--- a/speechx/speechx/common/base/common.h
+++ b/speechx/speechx/common/base/common.h
@@ -42,6 +42,8 @@
 #include <unordered_set>
 #include <utility>
 #include <vector>
+#include <future>
+#include <functional>
 
 #include "base/basic_types.h"
 #include "base/flags.h"