diff --git a/paddle/framework/backward.cc b/paddle/framework/backward.cc
index 8538ad9f0a95a19cba8bcf771166181793492eac..716e78f342ea5d7a5cb331e68fc7e7c6f7e4cfdf 100644
--- a/paddle/framework/backward.cc
+++ b/paddle/framework/backward.cc
@@ -13,6 +13,7 @@
    limitations under the License. */
 
 #include "paddle/framework/backward.h"
+#include <list>
 #include "paddle/framework/net.h"
 #include "paddle/framework/op_registry.h"
 
@@ -71,7 +72,7 @@ static std::shared_ptr<OperatorBase> BackwardImpl(
     return EmptyOp();
   }
 
-  // auto* net = new NetOp();
+  auto* net = new NetOp();
 
   if (forwardOp.IsNetOp()) {
     //! TODO(dzh)
@@ -93,29 +94,32 @@ static std::shared_ptr<OperatorBase> BackwardImpl(
     }
     // unique the duplicate name
     auto uid = uniq_id++;
-    std::unordered_map<size_t, OperatorBase> insert_postion;
+    // TODO(dzh): more comment
+    typedef std::pair<size_t, std::shared_ptr<OperatorBase>> Pos;
+    std::list<Pos> insert_postion;
     for (auto& dup_output_op : dup_output_ops) {
-      std::string& name = dup_output_op.first;
+      const std::string& name = dup_output_op.first;
       auto& dup_op = dup_output_op.second;
       if (dup_op.size() == 1) continue;
       std::vector<std::string> dup_outputs;
 
       for (size_t i = 0; i < dup_op.size(); ++i) {
         auto op_offset = dup_op[i];
-        net->ops_[op_offset].Rename(
-            name,
-            name + "@RENAME@" + std::to_string(uid) + "@" + std::to_string(i));
+        dup_outputs.push_back(name + "@RENAME@" + std::to_string(uid) + "@" +
+                              std::to_string(i));
+        net->ops_[op_offset]->Rename(name, dup_outputs.back());
       }
-      insert_postion[op_offset] =
-          OpRegistry::CreateOp("Add", {}, {dup_op->inputs_}, {});
-      net->AddOp("Add");
-      net->AddOp();
-      // process shared variable
-      // while(dup_op.size()) {
-      //
-      //  AddOp(OpRegistry::CreateOp("generic_add", {dup_outputs},
-      //                             {dup_op->inputs_}, {}));
-      //}
+      insert_postion.push_back(
+          {dup_op.back(),
+           OpRegistry::CreateOp(
+               "Add", {dup_outputs}, {name},
+               {{"input_format",
+                 std::vector<int>{0, (int)dup_outputs.size()}}})});
+    }
+    insert_postion.sort(
+        [](const Pos& l, const Pos& r) { return l.first > r.first; });
+    for (auto& pos : insert_postion) {
+      net->InsertOp(pos.first, pos.second);
     }
 
   } else {
diff --git a/paddle/framework/backward_test.cc b/paddle/framework/backward_test.cc
index 6f86b62b48d1d00d5c565241d5e78c57f1adf5db..0666bcc14cc3be9e1e9260e4c31cf4eec3a92e03 100644
--- a/paddle/framework/backward_test.cc
+++ b/paddle/framework/backward_test.cc
@@ -215,7 +215,7 @@ TEST(Backward, net_input_of_network_not_need_grad) {
   ASSERT_EQ(all_output.find("X" + f::OperatorBase::GRAD_VAR_SUFFIX()),
             all_output.end());
 
-  ASSERT_EQ(2, bwd_net->ops_.size());
+  ASSERT_EQ(2UL, bwd_net->ops_.size());
   ASSERT_TRUE(bwd_net->ops_[1]->IsNetOp());
   auto first_fc_grad = static_cast<f::NetOp *>(bwd_net->ops_[1].get());
   ASSERT_EQ(3, first_fc_grad->ops_.size());
@@ -333,4 +333,4 @@ TEST(Backward, linear_net_intermediate_variable_has_no_grad) {
   ASSERT_EQ(grad_fc.Input("W"), "w3");
   ASSERT_EQ(grad_fc.Input("b"), "b3");
   ASSERT_EQ(grad_fc.Input("Out"), "out3");
-}
\ No newline at end of file
+}
diff --git a/paddle/framework/net.cc b/paddle/framework/net.cc
index 403d96a22de87ce551ebd330a10434f9be7ff609..2cd378c6b21303d1a24206ba3010b0d035aaa766 100644
--- a/paddle/framework/net.cc
+++ b/paddle/framework/net.cc
@@ -74,27 +74,5 @@ std::string NetOp::DebugString() const {
 
 bool NetOp::IsNetOp() const { return true; }
 
-void NetOp::Rename(const std::unordered_map<
-                       std::string, std::vector<OpIdentity>>& dup_output_ops,
-                   size_t& uniq_id) {
-  for (auto& op : ops_) {
-    if (op->isNetOp()) {
-      op->Rename(dup_output_ops, uniq_id);
-    }
-    for (size_t i = 0; i < op->outputs_.size(); ++i) {
-      std::vector<std::string> dup_outputs;
-      if (op->outputs_[i] ==) {
-        op->outputs_[i] += std::to_string(uniq_id++);
-        dup_outputs.push_back(op->outputs_[i]);
-      }
-      // add duplicate output together. replace with AddOp
-      if (dup_outputs.size() >= 2) {
-        AddOp(OpRegistry::CreateOp("generic_add", {dup_outputs}, {op->inputs_},
-                                   {}));
-      }
-    }
-  }
-}
-
 }  // namespace framework
 }  // namespace paddle
diff --git a/paddle/framework/net.h b/paddle/framework/net.h
index bc55c8ee05d1b37317cd9c230e1fccaa1613eba4..9c7f0eab73b4171d085241324bf8521cd4064af7 100644
--- a/paddle/framework/net.h
+++ b/paddle/framework/net.h
@@ -49,11 +49,6 @@ class NetOp : public OperatorBase {
     }
   }
 
-  /**
-   * @brief rename duplicated output gradient name in Net
-   */
-  bool Rename(size_t& uniq_id);
-
   /**
    * @brief Run the network.
    *