diff --git a/python/paddle/fluid/dygraph/layers.py b/python/paddle/fluid/dygraph/layers.py
index c7c4df1fcf4f70dd6f2fdc05942bead926eefe18..58113808a9842f1922f83c8fdd91c9f59c8cbdc2 100644
--- a/python/paddle/fluid/dygraph/layers.py
+++ b/python/paddle/fluid/dygraph/layers.py
@@ -150,15 +150,11 @@ class Layer(core.Layer):
         Returns:
             list of :ref:`api_guide_Variable_en` : a list of Parameters.
         """
-        ret = [p for p in self._parameters.values()]
-        parameters_set = set(ret)
-        if include_sublayers:
-            for l in self._sub_layers.values():
-                for p in l.parameters(include_sublayers):
-                    if p in parameters_set:
-                        continue
-                    parameters_set.add(p)
-                    ret.append(p)
+        ret = [
+            param
+            for _, param in self.named_parameters(
+                include_sublayers=include_sublayers)
+        ]
         return ret
 
     def sublayers(self, include_sublayers=True):
@@ -170,11 +166,11 @@ class Layer(core.Layer):
         Returns:
             list of Layer : a list of sub layers.
         """
-        ret = [l for l in self._sub_layers.values()]
-        if include_sublayers:
-            for l in self._sub_layers.values():
-                for sub_l in l.sublayers(include_sublayers):
-                    ret.append(sub_l)
+        ret = [
+            layer
+            for _, layer in self.named_sublayers(
+                include_sublayers=include_sublayers)
+        ]
         return ret
 
     def named_parameters(self, prefix='', include_sublayers=True):
@@ -349,7 +345,12 @@ class Layer(core.Layer):
         Returns:
             Parameter: the parameter passed in.
         """
-        assert isinstance(parameter, framework.Parameter)
+        if parameter is None:
+            self._parameters[name] = None
+        elif not isinstance(parameter, framework.Parameter):
+            raise TypeError(
+                "parameter assignment requires Parameter or None, but got '{}'"
+                .format(type(parameter).__name__))
 
         if len(self._loaddict_holder) > 0:
             assert parameter.name in self._loaddict_holder, "Parameter not found, Can't not find [ {} ] in stat_dict".format(
@@ -376,8 +377,8 @@ class Layer(core.Layer):
 
         if isinstance(getattr(type(self), name, None), property):
             object.__setattr__(self, name, value)
+        params = self.__dict__.get('_parameters', None)
         if isinstance(value, framework.Parameter):
-            params = self.__dict__.get('_parameters', None)
             if params is None:
                 raise ValueError(
                     "super(YourLayer, self).__init__() should be called first")
@@ -389,16 +390,30 @@ class Layer(core.Layer):
 
             _remove_if_exist(self.__dict__, self._sub_layers)
             params[name] = value
-        elif isinstance(value, core.Layer):
-            layers = self.__dict__.get('_sub_layers', None)
-            if layers is None:
-                raise ValueError(
-                    "super(YourLayer, self).__init__() should be called first")
-
-            _remove_if_exist(self.__dict__, self._parameters)
-            layers[name] = value
+        elif params is not None and name in params:
+            if value is not None:
+                raise TypeError(
+                    "assignment to parameter '{}' should be of type Parameter or None, but got '{}'"
+                    .format(name, type(value).__name__))
+            params[name] = None
         else:
-            object.__setattr__(self, name, value)
+            layers = self.__dict__.get('_sub_layers', None)
+            if isinstance(value, core.Layer):
+                if layers is None:
+                    raise ValueError(
+                        "super(YourLayer, self).__init__() should be called first"
+                    )
+
+                _remove_if_exist(self.__dict__, self._parameters)
+                layers[name] = value
+            elif layers is not None and name in layers:
+                if value is not None:
+                    raise TypeError(
+                        "assignment to sublayer '{}' should be of type Layer or None, but got '{}'"
+                        .format(name, type(value).__name__))
+                layers[name] = None
+            else:
+                object.__setattr__(self, name, value)
 
     def __delattr__(self, name):
         if name in self._parameters:
diff --git a/python/paddle/fluid/tests/unittests/test_imperative_basic.py b/python/paddle/fluid/tests/unittests/test_imperative_basic.py
index d1a2d02747890047fcd914be09952ba459fb94e7..944d7bd3a85ad54020e71ec81dd6f4829a65bf92 100644
--- a/python/paddle/fluid/tests/unittests/test_imperative_basic.py
+++ b/python/paddle/fluid/tests/unittests/test_imperative_basic.py
@@ -497,6 +497,19 @@ class TestImperative(unittest.TestCase):
         self.assertTrue(hasattr(layer, "test_attr"))
         self.assertEqual(layer.test_attr, 1)
 
+        my_layer = MyLayer()
+        my_layer.w1 = my_layer.create_parameter([3, 3])
+        my_layer.add_parameter('w2', None)
+        self.assertEqual(len(my_layer.parameters()), 1)
+        self.assertRaises(TypeError, my_layer.__setattr__, 'w1', 'str')
+        my_layer.w1 = None
+        self.assertEqual(len(my_layer.parameters()), 0)
+        my_layer.l1 = fluid.dygraph.Linear(3, 3)
+        self.assertEqual(len(my_layer.sublayers()), 1)
+        self.assertRaises(TypeError, my_layer.__setattr__, 'l1', 'str')
+        my_layer.l1 = None
+        self.assertEqual(len(my_layer.sublayers()), 0)
+
 
 if __name__ == '__main__':
     unittest.main()