diff --git a/paddle/gserver/layers/MKLDNNLayer.h b/paddle/gserver/layers/MKLDNNLayer.h
index 907927f984f1a7cd4a72038515569251df48d56f..8d1271da2159cc994fef6fa3a1f4719fa21ca4d0 100644
--- a/paddle/gserver/layers/MKLDNNLayer.h
+++ b/paddle/gserver/layers/MKLDNNLayer.h
@@ -36,7 +36,7 @@ class MKLDNNLayer : public Layer {
 protected:
   // batch size
   int bs_;
-  // they sizes are always from the first input layer
+  // their sizes are always from the first input layer
   // input image channel, height and width
   int ic_, ih_, iw_;
   // output image channel, height and width
diff --git a/paddle/gserver/tests/test_MKLDNN.cpp b/paddle/gserver/tests/test_MKLDNN.cpp
index 42644e9601a82ea81c417adc6441edeb036998e2..56b523f220c2a405851b89db5f63e9aa50bfaaf7 100644
--- a/paddle/gserver/tests/test_MKLDNN.cpp
+++ b/paddle/gserver/tests/test_MKLDNN.cpp
@@ -315,7 +315,7 @@ TEST(MKLDNNLayer, AddtoLayer) {
 
 static void getMKLDNNConcatConfig(TestConfig& cfg,
                                   const std::vector<testImageDesc>& inputs) {
-  CHECK_GE(inputs.size(), 2) << "at least two inputs";
+  CHECK_GE(inputs.size(), 2UL) << "at least two inputs";
   int oc = inputs[0].ic;
   for (size_t i = 1; i < inputs.size(); ++i) {
     CHECK_EQ(inputs[i].bs, inputs[0].bs);
diff --git a/paddle/operators/beam_search_op.cc b/paddle/operators/beam_search_op.cc
index 17926a813d5b0b8ace6a1b20066cd0007703c696..8c3e2a303fb8f12a8886c11cf112b859a6db7bcf 100644
--- a/paddle/operators/beam_search_op.cc
+++ b/paddle/operators/beam_search_op.cc
@@ -139,7 +139,7 @@ bool BeamSearch::NextItemSet(std::vector<BeamSearch::Item> *items) {
   items->reserve(framework::product(ids.dims()));
   for (size_t offset = abs_lod[lod_level_][sent_offset_];
        offset < abs_lod[lod_level_][sent_offset_ + 1]; offset++) {
-    for (int d = 0; d < instance_dim; d++) {
+    for (size_t d = 0; d < instance_dim; d++) {
       const size_t dim_offset = offset * instance_dim + d;
       items->emplace_back(offset, ids_data[dim_offset],
                           scores_data[dim_offset]);
diff --git a/paddle/trainer/Trainer.cpp b/paddle/trainer/Trainer.cpp
index 88e684849df6fbfe4042b92bdb76ef98159eecea..3e4a2b5fa8a3981f6362edc1dc61ae1616e257ef 100644
--- a/paddle/trainer/Trainer.cpp
+++ b/paddle/trainer/Trainer.cpp
@@ -138,7 +138,7 @@ void Trainer::init(const std::shared_ptr<TrainerConfigHelper>& config,
   }
 
   if (FLAGS_use_mkldnn) {
-    CHECK_EQ(FLAGS_trainer_count, 1UL) << "MKLDNN only need 1 trainer";
+    CHECK_EQ(FLAGS_trainer_count, 1) << "MKLDNN only need 1 trainer";
   }
 
   if (testing) {