diff --git a/paddle/fluid/framework/data_set.cc b/paddle/fluid/framework/data_set.cc
index ebe7f6caca567b8f7bb32eb90fbda4cd0c3a3564..514bc8ba9ebf1f1a394588378f2ef66c05013599 100644
--- a/paddle/fluid/framework/data_set.cc
+++ b/paddle/fluid/framework/data_set.cc
@@ -646,10 +646,12 @@ void MultiSlotDataset::MergeByInsId() {
   }
   auto multi_slot_desc = data_feed_desc_.multi_slot_desc();
   std::vector<std::string> use_slots;
+  std::vector<bool> use_slots_is_dense;
   for (int i = 0; i < multi_slot_desc.slots_size(); ++i) {
     const auto& slot = multi_slot_desc.slots(i);
     if (slot.is_used()) {
       use_slots.push_back(slot.name());
+      use_slots_is_dense.push_back(slot.is_dense());
     }
   }
   CHECK(multi_output_channel_.size() != 0);  // NOLINT
@@ -679,6 +681,11 @@ void MultiSlotDataset::MergeByInsId() {
   std::unordered_set<uint16_t> all_float;
   std::unordered_set<uint16_t> local_uint64;
   std::unordered_set<uint16_t> local_float;
+  std::unordered_map<uint16_t, std::vector<FeatureItem>> all_dense_uint64;
+  std::unordered_map<uint16_t, std::vector<FeatureItem>> all_dense_float;
+  std::unordered_map<uint16_t, std::vector<FeatureItem>> local_dense_uint64;
+  std::unordered_map<uint16_t, std::vector<FeatureItem>> local_dense_float;
+  std::unordered_map<uint16_t, bool> dense_empty;
 
   VLOG(3) << "recs.size() " << recs.size();
   for (size_t i = 0; i < recs.size();) {
@@ -696,6 +703,8 @@ void MultiSlotDataset::MergeByInsId() {
 
     all_int64.clear();
     all_float.clear();
+    all_dense_uint64.clear();
+    all_dense_float.clear();
     bool has_conflict_slot = false;
     uint16_t conflict_slot = 0;
 
@@ -703,12 +712,61 @@ void MultiSlotDataset::MergeByInsId() {
     rec.ins_id_ = recs[i].ins_id_;
     rec.content_ = recs[i].content_;
 
+    for (size_t k = i; k < j; k++) {
+      dense_empty.clear();
+      local_dense_uint64.clear();
+      local_dense_float.clear();
+      for (auto& feature : recs[k].uint64_feasigns_) {
+        uint16_t slot = feature.slot();
+        if (!use_slots_is_dense[slot]) {
+          continue;
+        }
+        local_dense_uint64[slot].push_back(feature);
+        if (feature.sign().uint64_feasign_ != 0) {
+          dense_empty[slot] = false;
+        } else if (dense_empty.find(slot) == dense_empty.end() &&
+                   all_dense_uint64.find(slot) == all_dense_uint64.end()) {
+          dense_empty[slot] = true;
+        }
+      }
+      for (auto& feature : recs[k].float_feasigns_) {
+        uint16_t slot = feature.slot();
+        if (!use_slots_is_dense[slot]) {
+          continue;
+        }
+        local_dense_float[slot].push_back(feature);
+        if (fabs(feature.sign().float_feasign_) >= 1e-6) {
+          dense_empty[slot] = false;
+        } else if (dense_empty.find(slot) == dense_empty.end() &&
+                   all_dense_float.find(slot) == all_dense_float.end()) {
+          dense_empty[slot] = true;
+        }
+      }
+      for (auto& p : dense_empty) {
+        if (local_dense_uint64.find(p.first) != local_dense_uint64.end()) {
+          all_dense_uint64[p.first] = std::move(local_dense_uint64[p.first]);
+        } else if (local_dense_float.find(p.first) != local_dense_float.end()) {
+          all_dense_float[p.first] = std::move(local_dense_float[p.first]);
+        }
+      }
+    }
+    for (auto& f : all_dense_uint64) {
+      rec.uint64_feasigns_.insert(rec.uint64_feasigns_.end(), f.second.begin(),
+                                  f.second.end());
+    }
+    for (auto& f : all_dense_float) {
+      rec.float_feasigns_.insert(rec.float_feasigns_.end(), f.second.begin(),
+                                 f.second.end());
+    }
+
     for (size_t k = i; k < j; k++) {
       local_uint64.clear();
       local_float.clear();
       for (auto& feature : recs[k].uint64_feasigns_) {
         uint16_t slot = feature.slot();
-        if (all_int64.find(slot) != all_int64.end()) {
+        if (use_slots_is_dense[slot]) {
+          continue;
+        } else if (all_int64.find(slot) != all_int64.end()) {
           has_conflict_slot = true;
           conflict_slot = slot;
           break;
@@ -723,7 +781,9 @@ void MultiSlotDataset::MergeByInsId() {
 
       for (auto& feature : recs[k].float_feasigns_) {
         uint16_t slot = feature.slot();
-        if (all_float.find(slot) != all_float.end()) {
+        if (use_slots_is_dense[slot]) {
+          continue;
+        } else if (all_float.find(slot) != all_float.end()) {
           has_conflict_slot = true;
           conflict_slot = slot;
           break;
diff --git a/python/paddle/fluid/tests/unittests/test_dataset.py b/python/paddle/fluid/tests/unittests/test_dataset.py
index 6dc28b3e783558964c77687306896c7562e093eb..d2b7e508a589fb23407dc598d21a9678cbbdee18 100644
--- a/python/paddle/fluid/tests/unittests/test_dataset.py
+++ b/python/paddle/fluid/tests/unittests/test_dataset.py
@@ -264,6 +264,72 @@ class TestDataset(unittest.TestCase):
         os.remove("./test_in_memory_dataset_masterpatch_a.txt")
         os.remove("./test_in_memory_dataset_masterpatch_b.txt")
 
+    def test_in_memory_dataset_masterpatch1(self):
+        """
+        Testcase for InMemoryDataset from create to run.
+        """
+        with open("test_in_memory_dataset_masterpatch1_a.txt", "w") as f:
+            data = "1 id1 1 1 2 3 3 4 5 5 5 5 1 1\n"
+            data += "1 id1 1 2 2 3 4 4 6 6 6 6 1 2\n"
+            data += "1 id2 1 1 1 1 1 0 1 0\n"
+            data += "1 id3 1 0 1 0 1 1 1 1\n"
+            data += "1 id3 1 1 1 1 1 0 1 0\n"
+            data += "1 id4 1 0 1 0 1 1 1 1\n"
+            data += "1 id4 1 0 1 0 1 1 1 1\n"
+            data += "1 id5 1 1 1 1 1 0 1 0\n"
+            data += "1 id5 1 1 1 1 1 0 1 0\n"
+            f.write(data)
+        with open("test_in_memory_dataset_masterpatch1_b.txt", "w") as f:
+            data = "1 id6 1 4 2 3 3 4 5 5 5 5 1 4\n"
+            data += "1 id6 1 1 2 3 4 4 6 6 6 6 1 5\n"
+            data += "1 id6 1 6 2 3 5 4 7 7 7 7 1 6\n"
+            data += "1 id6 1 7 2 3 6 4 8 8 8 8 1 7\n"
+            f.write(data)
+
+        slots_vars = []
+        train_program = fluid.Program()
+        startup_program = fluid.Program()
+        with fluid.program_guard(train_program, startup_program):
+            var1 = fluid.layers.data(
+                name="slot1", shape=[1], dtype="int64", lod_level=0)
+            var2 = fluid.layers.data(
+                name="slot2", shape=[1], dtype="int64", lod_level=0)
+            var3 = fluid.layers.data(
+                name="slot3", shape=[1], dtype="float32", lod_level=0)
+            var4 = fluid.layers.data(
+                name="slot4", shape=[1], dtype="float32", lod_level=0)
+            slots_vars = [var1, var2, var3, var4]
+
+        dataset = fluid.DatasetFactory().create_dataset("InMemoryDataset")
+        dataset.set_batch_size(32)
+        dataset.set_thread(1)
+        dataset.set_parse_ins_id(True)
+        dataset.set_filelist([
+            "test_in_memory_dataset_masterpatch1_a.txt",
+            "test_in_memory_dataset_masterpatch1_b.txt"
+        ])
+        dataset.set_pipe_command("cat")
+        dataset.set_use_var(slots_vars)
+        dataset.load_into_memory()
+        dataset.local_shuffle()
+
+        exe = fluid.Executor(fluid.CPUPlace())
+        exe.run(startup_program)
+
+        for i in range(2):
+            try:
+                exe.train_from_dataset(train_program, dataset)
+            except ImportError as e:
+                pass
+            except Exception as e:
+                self.assertTrue(False)
+
+        dataset.set_merge_by_lineid(2)
+        dataset.dataset.merge_by_lineid()
+
+        os.remove("./test_in_memory_dataset_masterpatch1_a.txt")
+        os.remove("./test_in_memory_dataset_masterpatch1_b.txt")
+
     def test_in_memory_dataset_run_2(self):
         """
         Testcase for InMemoryDataset from create to run.