diff --git a/mindarmour/diff_privacy/mechanisms/mechanisms.py b/mindarmour/diff_privacy/mechanisms/mechanisms.py
index dd8f5da4ceef44e9884aa22a85f4b41a0886664a..44aaea49e17e3addc3b118e87a32fe86e6bd7fac 100644
--- a/mindarmour/diff_privacy/mechanisms/mechanisms.py
+++ b/mindarmour/diff_privacy/mechanisms/mechanisms.py
@@ -159,7 +159,10 @@ class AdaGaussianRandom(Mechanisms):
         alpha = check_param_type('alpha', alpha, float)
         self._alpha = Tensor(np.array(alpha, np.float32))
 
-        self._decay_policy = check_param_type('decay_policy', decay_policy, str)
+        if decay_policy not in ['Time', 'Step']:
+            raise NameError("The decay_policy must be in ['Time', 'Step'], but "
+                            "get {}".format(decay_policy))
+        self._decay_policy = decay_policy
         self._mean = 0.0
         self._sub = P.Sub()
         self._mul = P.Mul()
diff --git a/mindarmour/utils/_check_param.py b/mindarmour/utils/_check_param.py
index 06a37c66ca3c977f59a843ae38568439111a7426..36ebc8724d667f71dc7232faf044f908ab7a5e5b 100644
--- a/mindarmour/utils/_check_param.py
+++ b/mindarmour/utils/_check_param.py
@@ -43,7 +43,7 @@ def check_param_type(arg_name, arg_value, valid_type):
                                                  valid_type,
                                                  type(arg_value).__name__)
         LOGGER.error(TAG, msg)
-        raise ValueError(msg)
+        raise TypeError(msg)
 
     return arg_value
 
@@ -54,7 +54,7 @@ def check_param_multi_types(arg_name, arg_value, valid_types):
         msg = 'type of {} must be in {}, but got {}' \
             .format(arg_name, valid_types, type(arg_value).__name__)
         LOGGER.error(TAG, msg)
-        raise ValueError(msg)
+        raise TypeError(msg)
 
     return arg_value
 
@@ -157,7 +157,7 @@ def check_numpy_param(arg_name, arg_value):
         msg = 'type of {} must be in (list, tuple, numpy.ndarray)'.format(
             arg_name)
         LOGGER.error(TAG, msg)
-        raise ValueError(msg)
+        raise TypeError(msg)
     return arg_value
 
 
diff --git a/tests/ut/python/attacks/test_iterative_gradient_method.py b/tests/ut/python/attacks/test_iterative_gradient_method.py
index 3a9fcb024a94634c08770c2be0ce0c0b524f113c..34cc2e384be7b02bbdefe7bfed2dc54901797711 100644
--- a/tests/ut/python/attacks/test_iterative_gradient_method.py
+++ b/tests/ut/python/attacks/test_iterative_gradient_method.py
@@ -167,7 +167,7 @@ def test_momentum_diverse_input_iterative_method():
 @pytest.mark.env_card
 @pytest.mark.component_mindarmour
 def test_error():
-    with pytest.raises(ValueError):
+    with pytest.raises(TypeError):
         # check_param_multi_types
         assert IterativeGradientMethod(Net(), bounds=None)
     attack = IterativeGradientMethod(Net(), bounds=(0.0, 1.0))
diff --git a/tests/ut/python/detectors/test_region_based_detector.py b/tests/ut/python/detectors/test_region_based_detector.py
index c9587498cf0448c3ba1e43da5c415a6f354ee963..f4b891acbdc1261a664392041fa5e19055b8c10d 100644
--- a/tests/ut/python/detectors/test_region_based_detector.py
+++ b/tests/ut/python/detectors/test_region_based_detector.py
@@ -100,16 +100,16 @@ def test_value_error():
     with pytest.raises(ValueError):
         assert RegionBasedDetector(model, search_step=0)
 
-    with pytest.raises(ValueError):
+    with pytest.raises(TypeError):
         assert RegionBasedDetector(model, sparse='False')
 
     detector = RegionBasedDetector(model)
-    with pytest.raises(ValueError):
+    with pytest.raises(TypeError):
         # radius must not empty
         assert detector.detect(adv)
 
     radius = detector.fit(ori, labels)
     detector.set_radius(radius)
-    with pytest.raises(ValueError):
+    with pytest.raises(TypeError):
         # adv type should be in (list, tuple, numpy.ndarray)
         assert detector.detect(adv.tostring())