diff --git a/paddle/fluid/operators/detection_map_op.h b/paddle/fluid/operators/detection_map_op.h
index dd1ab85fd8d0c8170afcd9dd2a49ee55c41dc8be..dd5d138a1e979826d59c4731920379b030e3b492 100644
--- a/paddle/fluid/operators/detection_map_op.h
+++ b/paddle/fluid/operators/detection_map_op.h
@@ -76,8 +76,8 @@ class DetectionMAPOpKernel : public framework::OpKernel<T> {
     auto ap_type = GetAPType(ctx.Attr<std::string>("ap_type"));
     int class_num = ctx.Attr<int>("class_num");
 
-    auto label_lod = in_label->lod();
-    auto detect_lod = in_detect->lod();
+    auto& label_lod = in_label->lod();
+    auto& detect_lod = in_detect->lod();
     PADDLE_ENFORCE_EQ(label_lod.size(), 1UL,
                       "Only support one level sequence now.");
     PADDLE_ENFORCE_EQ(label_lod[0].size(), detect_lod[0].size(),
@@ -166,11 +166,11 @@ class DetectionMAPOpKernel : public framework::OpKernel<T> {
     auto labels = framework::EigenTensor<T, 2>::From(input_label);
     auto detect = framework::EigenTensor<T, 2>::From(input_detect);
 
-    auto label_lod = input_label.lod();
-    auto detect_lod = input_detect.lod();
+    auto& label_lod = input_label.lod();
+    auto& detect_lod = input_detect.lod();
 
     int batch_size = label_lod[0].size() - 1;
-    auto label_index = label_lod[0];
+    auto& label_index = label_lod[0];
 
     for (int n = 0; n < batch_size; ++n) {
       std::map<int, std::vector<Box>> boxes;
@@ -274,7 +274,6 @@ class DetectionMAPOpKernel : public framework::OpKernel<T> {
 
     output_true_pos->set_lod(true_pos_lod);
     output_false_pos->set_lod(false_pos_lod);
-    return;
   }
 
   void GetInputPos(const framework::Tensor& input_pos_count,
@@ -292,7 +291,7 @@ class DetectionMAPOpKernel : public framework::OpKernel<T> {
     auto SetData = [](const framework::LoDTensor& pos_tensor,
                       std::map<int, std::vector<std::pair<T, int>>>& pos) {
       const T* pos_data = pos_tensor.data<T>();
-      auto pos_data_lod = pos_tensor.lod()[0];
+      auto& pos_data_lod = pos_tensor.lod()[0];
       for (size_t i = 0; i < pos_data_lod.size() - 1; ++i) {
         for (size_t j = pos_data_lod[i]; j < pos_data_lod[i + 1]; ++j) {
           T score = pos_data[j * 2];
@@ -317,20 +316,23 @@ class DetectionMAPOpKernel : public framework::OpKernel<T> {
       std::map<int, std::vector<std::pair<T, int>>>* false_pos) const {
     int batch_size = gt_boxes.size();
     for (int n = 0; n < batch_size; ++n) {
-      auto image_gt_boxes = gt_boxes[n];
-      for (auto it = image_gt_boxes.begin(); it != image_gt_boxes.end(); ++it) {
+      auto& image_gt_boxes = gt_boxes[n];
+      for (auto& image_gt_box : image_gt_boxes) {
         size_t count = 0;
-        auto labeled_bboxes = it->second;
+        auto& labeled_bboxes = image_gt_box.second;
         if (evaluate_difficult) {
           count = labeled_bboxes.size();
         } else {
-          for (size_t i = 0; i < labeled_bboxes.size(); ++i)
-            if (!(labeled_bboxes[i].is_difficult)) ++count;
+          for (auto& box : labeled_bboxes) {
+            if (!box.is_difficult) {
+              ++count;
+            }
+          }
         }
         if (count == 0) {
           continue;
         }
-        int label = it->first;
+        int label = image_gt_box.first;
         if (label_pos_count->find(label) == label_pos_count->end()) {
           (*label_pos_count)[label] = count;
         } else {
diff --git a/python/paddle/fluid/tests/unittests/op_test.py b/python/paddle/fluid/tests/unittests/op_test.py
index 56a242b996f67aa4b9c858ab8aaeb1c1cd3bcf60..cefaa3892023f1709e76ebea89bfabea6c16ed34 100644
--- a/python/paddle/fluid/tests/unittests/op_test.py
+++ b/python/paddle/fluid/tests/unittests/op_test.py
@@ -348,7 +348,7 @@ class OpTest(unittest.TestCase):
                         actual_t, expect_t, atol=atol, equal_nan=equal_nan),
                     "Output (" + out_name + ") has diff at " + str(place) +
                     "\nExpect " + str(expect_t) + "\n" + "But Got" +
-                    str(actual_t))
+                    str(actual_t) + " in class " + self.__class__.__name__)
                 if isinstance(expect, tuple):
                     self.assertListEqual(actual.recursive_sequence_lengths(),
                                          expect[1], "Output (" + out_name +
diff --git a/python/paddle/fluid/tests/unittests/test_detection_map_op.py b/python/paddle/fluid/tests/unittests/test_detection_map_op.py
index f6eb8f2c6d8b94f92e24ff789c91efb53a645a46..0c5343a97d5ef0f97fc6b144dfc82174eacb8573 100644
--- a/python/paddle/fluid/tests/unittests/test_detection_map_op.py
+++ b/python/paddle/fluid/tests/unittests/test_detection_map_op.py
@@ -20,6 +20,7 @@ import six
 import sys
 import collections
 import math
+import paddle.fluid as fluid
 from op_test import OpTest
 
 
@@ -32,7 +33,7 @@ class TestDetectionMAPOp(OpTest):
         self.detect = np.array(self.detect).astype('float32')
         self.mAP = np.array(self.mAP).astype('float32')
 
-        if (len(self.class_pos_count) > 0):
+        if len(self.class_pos_count) > 0:
             self.class_pos_count = np.array(self.class_pos_count).astype(
                 'int32')
             self.true_pos = np.array(self.true_pos).astype('float32')
@@ -273,7 +274,7 @@ class TestDetectionMAPOp11Point(TestDetectionMAPOp):
 class TestDetectionMAPOpMultiBatch(TestDetectionMAPOp):
     def init_test_case(self):
         super(TestDetectionMAPOpMultiBatch, self).init_test_case()
-        self.class_pos_count = [0, 2, 1]
+        self.class_pos_count = [0, 2, 1, 0]
         self.true_pos_lod = [[0, 3, 2]]
         self.true_pos = [[0.7, 1.], [0.3, 0.], [0.2, 1.], [0.8, 0.], [0.1, 1.]]
         self.false_pos_lod = [[0, 3, 2]]