diff --git a/parl/core/fluid/model.py b/parl/core/fluid/model.py
index 7c23eda633bf7487ac577de9d50590c2e15626e9..38d653ad20275d281a1bca4cf63d1198475a8696 100644
--- a/parl/core/fluid/model.py
+++ b/parl/core/fluid/model.py
@@ -273,33 +273,33 @@ class Model(ModelBase):
             set_value(param_name, weight, is_gpu_available)
 
     def _get_parameter_names(self, obj):
-        """ Recursively get parameter names in a model and its child attributes.
+        """ Recursively get parameter names in an object.
 
         Args:
-            obj (``parl.Model``): an instance of ``Model``
+            obj (Object): any object
 
         Returns:
-            parameter_names (list): all parameter names in this model.
+            parameter_names (list): all parameter names in this object.
         """
 
         parameter_names = []
-        for attr in sorted(obj.__dict__.keys()):
-            val = getattr(obj, attr)
-            if isinstance(val, Model):
+        if isinstance(obj, Model):
+            for attr in sorted(obj.__dict__.keys()):
+                val = getattr(obj, attr)
                 parameter_names.extend(self._get_parameter_names(val))
-            elif isinstance(val, LayerFunc):
-                for attr in val.attr_holder.sorted():
-                    if attr:
-                        parameter_names.append(attr.name)
-            elif isinstance(val, tuple) or isinstance(val, list):
-                for x in val:
-                    parameter_names.extend(self._get_parameter_names(x))
-            elif isinstance(val, dict):
-                for x in list(val.values()):
-                    parameter_names.extend(self._get_parameter_names(x))
-            else:
-                # for any other type, won't be handled. E.g. set
-                pass
+        elif isinstance(obj, LayerFunc):
+            for attr in obj.attr_holder.sorted():
+                if attr:
+                    parameter_names.append(attr.name)
+        elif isinstance(obj, tuple) or isinstance(obj, list):
+            for x in obj:
+                parameter_names.extend(self._get_parameter_names(x))
+        elif isinstance(obj, dict):
+            for x in list(obj.values()):
+                parameter_names.extend(self._get_parameter_names(x))
+        else:
+            # for any other type, won't be handled. E.g. set
+            pass
         return parameter_names
 
     def _get_parameter_pairs(self, src, target):
diff --git a/parl/core/fluid/tests/model_base_test_.py b/parl/core/fluid/tests/model_base_test_.py
index dbab50abaf4218907c1c021ca36f8f90e686ef21..82adbfbe3eb3fe5ce339c6ccef7bac697a795055 100644
--- a/parl/core/fluid/tests/model_base_test_.py
+++ b/parl/core/fluid/tests/model_base_test_.py
@@ -84,6 +84,42 @@ class TestModel4(parl.Model):
         return out
 
 
+class TestModel6(parl.Model):
+    def __init__(self):
+        self.fc1 = layers.fc(
+            size=256,
+            act=None,
+            param_attr=ParamAttr(name='fc1.w'),
+            bias_attr=ParamAttr(name='fc1.b'))
+        self.fc_tuple = (layers.fc(
+            size=128,
+            act=None,
+            param_attr=ParamAttr(name='fc2.w'),
+            bias_attr=ParamAttr(name='fc2.b')), (layers.fc(
+                size=1,
+                act=None,
+                param_attr=ParamAttr(name='fc3.w'),
+                bias_attr=ParamAttr(name='fc3.b')), 10), 10)
+        self.fc_dict = {
+            'k1':
+            layers.fc(
+                size=128,
+                act=None,
+                param_attr=ParamAttr(name='fc4.w'),
+                bias_attr=ParamAttr(name='fc4.b')),
+            'k2': {
+                'k22':
+                layers.fc(
+                    size=1,
+                    act=None,
+                    param_attr=ParamAttr(name='fc5.w'),
+                    bias_attr=ParamAttr(name='fc5.b'))
+            },
+            'k3':
+            1,
+        }
+
+
 class ModelBaseTest(unittest.TestCase):
     def setUp(self):
         self.model = TestModel()
@@ -139,6 +175,14 @@ class ModelBaseTest(unittest.TestCase):
             set(self.model.parameters()),
             set(['fc1.w', 'fc1.b', 'fc2.w', 'fc2.b', 'fc3.w', 'fc3.b']))
 
+        model2 = TestModel6()
+        self.assertSetEqual(
+            set(model2.parameters()),
+            set([
+                'fc1.w', 'fc1.b', 'fc2.w', 'fc2.b', 'fc3.w', 'fc3.b', 'fc4.w',
+                'fc4.b', 'fc5.w', 'fc5.b'
+            ]))
+
     def test_sync_weights_in_one_program(self):
         pred_program = fluid.Program()
         with fluid.program_guard(pred_program):