diff --git a/python/paddle/incubate/autograd/primx.py b/python/paddle/incubate/autograd/primx.py
index a69bce3c37bc43f5c39f8b0ca560c17fecfcafa7..6a5e4ae6fc366ad5197b40cdc487e86ddce005a5 100644
--- a/python/paddle/incubate/autograd/primx.py
+++ b/python/paddle/incubate/autograd/primx.py
@@ -684,7 +684,7 @@ def _lower_composite(block, blacklist=[]):
             del block.vars[var_name]
         block._sync_with_cpp()
 
-        # composite ops may contain other ops, thus, call _lower_composite again.
+        # composite ops may contain other composite ops, thus, call _lower_composite again.
         if change:
             _lower_composite(block, blacklist)
         return
diff --git a/python/paddle/incubate/autograd/utils.py b/python/paddle/incubate/autograd/utils.py
index 90bdb78336dc4a257e39c7ae37f3babf2a6cca0f..c011c7495e6ac269ea3eccb3045b3fe21fe292ba 100644
--- a/python/paddle/incubate/autograd/utils.py
+++ b/python/paddle/incubate/autograd/utils.py
@@ -169,6 +169,7 @@ def _get_args_values(op, phi_name):
         arg_type, arg_name = _solve_arg(item)
         op_content = op_map[op.type]
         if arg_type in ("Tensor", "Tensor[]"):
+            # assume Tensor type must belong to inputs
             if (
                 "inputs" in op_content.keys()
                 and arg_name in op_content["inputs"].keys()
@@ -182,7 +183,9 @@ def _get_args_values(op, phi_name):
                 "attrs" in op_content.keys()
                 and arg_name in op_content["attrs"].keys()
             ):
-                attrs.append(op.attr(op_content["attrs"][arg_name]))
+                arg_name = op_content["attrs"][arg_name]
+            if arg_name not in op.attr_names:
+                attrs.append(None)
             else:
                 attrs.append(op.attr(arg_name))
 
@@ -203,7 +206,12 @@ def prepare_python_api_arguments(op):
         else:
             phi_name = op.type
         inputs, attrs = _get_args_values(op, phi_name)
-        res = [get_var_block(op.block, op.input(n)) for n in inputs]
+        res = []
+        for item in inputs:
+            if item in op.input_names:
+                res.append(get_var_block(op.block, op.input(item)))
+            else:
+                res.append(None)
         if attrs:
             res.extend(attrs)
         return res