diff --git a/hobbit_core/flask_hobbit/db.py b/hobbit_core/flask_hobbit/db.py
index 496eb0b..f1282fb 100644
--- a/hobbit_core/flask_hobbit/db.py
+++ b/hobbit_core/flask_hobbit/db.py
@@ -1,5 +1,5 @@
 # -*- encoding: utf-8 -*-
-import enum
+from enum import Enum, EnumMeta
 import six
 
 from sqlalchemy import Integer, Column, ForeignKey, func, DateTime
@@ -61,7 +61,28 @@ def reference_col(tablename, nullable=False, pk_name='id', **kwargs):
         nullable=nullable, **kwargs)
 
 
-class EnumExt(enum.Enum):
+class EnumExtMeta(EnumMeta):
+
+    def __new__(cls, name, bases, attrs):
+        obj = super(EnumExtMeta, cls).__new__(cls, name, bases, attrs)
+
+        keys, values = set(), set()
+        for name, member in obj.__members__.items():
+            member = member.value
+            if not isinstance(member, tuple) or len(member) != 2:
+                raise TypeError(
+                    'EnumExt member must be tuple type and length equal 2.')
+            key, value = member
+            if key in keys or value in values:
+                raise ValueError('duplicate values found: `{}`, please check '
+                                 'key or value.'.format(member))
+            keys.add(key)
+            values.add(key)
+
+        return obj
+
+
+class EnumExt(six.with_metaclass(EnumExtMeta, Enum)):
     """ Extension for serialize/deserialize sqlalchemy enum field.
 
     Be sure ``type(key)`` is ``int`` and ``type(value)`` is ``str``
diff --git a/tests/test_db.py b/tests/test_db.py
index 8764000..b9d4946 100644
--- a/tests/test_db.py
+++ b/tests/test_db.py
@@ -8,6 +8,19 @@
 
 class TestEnumExt(BaseTest):
 
+    def test_key_index(self):
+        msg = "EnumExt member must be tuple type and length equal 2."
+        with pytest.raises(TypeError, message=msg):
+            class ErrTypeEnum(db.EnumExt):
+                CREATED = (0, u'新建', 'dda')
+
+        msg = "ValueError: duplicate values found: `(0, '已完成')`, " + \
+            "please check key or value."
+        with pytest.raises(ValueError, message=msg):
+            class ErrEnum(db.EnumExt):
+                CREATED = (0, u'新建')
+                FINISHED = (0, u'已完成')
+
     @pytest.fixture
     def TaskState(self):
         class _TaskState(db.EnumExt):
diff --git a/tox.ini b/tox.ini
index ed926ee..e3e46ef 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,6 +5,7 @@ envlist = py27,py36,py37
 deps =
     pytest
     pytest-cov
+    pytest-env
     flake8
     py27: ipython==5.8.0
 commands =