diff --git a/run.py b/run.py
index 553d3e9..df8eb7e 100755
--- a/run.py
+++ b/run.py
@@ -7,14 +7,21 @@
 import argparse
 import json
 import time
+import os
+import tempfile
 
-import ip
 from dns import alidns, dnspod
+from util import ip
+from util.cache import Cache
 
 DNS = dnspod
+CACHE_FILE = os.path.join(tempfile.gettempdir(), 'ddns.cache')
 
 
 def get_config(key=None, default=None, file="config.json"):
+    """
+    读取配置
+    """
     if not hasattr(get_config, "config"):
         try:
             with open(file) as configfile:
@@ -27,31 +34,38 @@ def get_config(key=None, default=None, file="config.json"):
         return get_config.config
 
 
-def update():
-    print "=" * 25 + " " + time.ctime() + " " + "=" * 25
-    index4 = get_config('index4') or "default"
-    if str(index4).isdigit():
-        ipv4 = ip.local_v4(index4)
+def update_ip(Type, cache):
+    """
+    更新IP
+    """
+    ipname = 'ipv' + Type
+    domains = get_config(ipname)
+    if not domains:
+        return None
+
+    index = get_config('index' + Type) or "default"
+    if str(index).isdigit():
+        value = getattr(ip, "local_v" + Type)(index)
+
     else:
-        ipv4 = getattr(ip, index4 + "_v4")()
-    print 'update ipv4 to:', ipv4
-    if ipv4 != None:
-        for domain in get_config('ipv4'):
-            print DNS.update_record(domain, ipv4, 'A')
+        value = getattr(ip, index + "_v" + Type)()
 
-    v6_domains = get_config("ipv6") or "default"
-    if len(v6_domains) > 0:
-        index6 = get_config('index6')
-        if str(index6).isdigit():
-            ipv6 = ip.local_v6(index6)
-        else:
-            ipv6 = getattr(ip, index6 + "_v6")()
-        print 'update ipv6 to:', ipv6
-        if ipv6 != None:
-            for domain in v6_domains:
-                print DNS.update_record(domain, ipv6, 'AAAA')
+    if value is None:
+        return False
+    elif value == cache[ipname]:
+        print '.',
+    else:
+        cache[ipname] = value
+        print 'update %s to: %s' % (ipname, value)
+        record_type = (Type == '4') and 'A' or 'AAAA'
+        for domain in domains:
+            print DNS.update_record(domain, value, record_type=record_type)
 
-if __name__ == '__main__':
+
+def main():
+    """
+    更新
+    """
     parser = argparse.ArgumentParser()
     parser.add_argument('-c', default="config.json")
     get_config(file=parser.parse_args().c)
@@ -60,4 +74,14 @@ if __name__ == '__main__':
     DNS.ID, DNS.TOKEN = get_config('id'), get_config('token')
     DNS.PROXY = get_config('proxy')
     ip.DEBUG = get_config('debug')
-    update()
+
+    cache = Cache(CACHE_FILE)
+    if len(cache) < 1:
+        print "=" * 25 + " " + time.ctime() + " " + "=" * 25
+
+    update_ip('4', cache)
+    update_ip('6', cache)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/util/__init__.py b/util/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/util/cache.py b/util/cache.py
new file mode 100644
index 0000000..8dde6bc
--- /dev/null
+++ b/util/cache.py
@@ -0,0 +1,139 @@
+# -*- coding: utf-8 -*-
+r"""
+cache module
+文件缓存
+"""
+
+import logging as LOG
+import os
+import pickle
+import time
+
+try:
+    from collections.abc import MutableMapping
+except ImportError:
+    # Python 2 imports
+    from collections import MutableMapping
+
+
+class Cache(MutableMapping):
+    """
+    using file to Cache data as dictionary
+    """
+
+    def __init__(self, path, sync=False):
+        self.__data = {}
+        self.__filename = path
+        self.__sync = sync
+        self.__changed = False
+        self.load()
+
+    @property
+    def time(self):
+        """
+        缓存修改时间
+        """
+        return self.__time
+
+    def load(self, path=None):
+        """
+        load data from path
+        """
+        if not path:
+            path = self.__filename
+
+        LOG.debug('load cache data from %s', path)
+        if os.path.isfile(path):
+            with open(self.__filename, 'r') as data:
+                self.__data = pickle.load(data)
+            self.__time = os.stat(path).st_mtime
+        else:
+            LOG.info('cache file not exist')
+            self.__data = {}
+            self.__time = time.time()
+        return self
+
+    def data(self, key=None, default=None):
+        """
+        获取当前字典或者制定得键值
+        """
+        if self.__sync:
+            self.load()
+
+        if key is None:
+            return self.__data
+        else:
+            return self.__data.get(key, default)
+
+    def sync(self):
+        """Sync the write buffer with the cache files and clear the buffer.
+        """
+        if self.__changed:
+            with open(self.__filename, 'w') as data:
+                pickle.dump(self.__data, data)
+                LOG.debug('save cache data to %s', self.__filename)
+            self.__changed = False
+        return self
+
+    def close(self):
+        """Sync the write buffer, then close the cache.
+        If a closed :class:`FileCache` object's methods are called, a
+        :exc:`ValueError` will be raised.
+        """
+        self.sync()
+        del self.__data
+        del self.__filename
+        del self.__time
+        self.__sync = False
+
+    def __setitem__(self, key, value):
+        if self.data(key) != value:
+            self.__data[key] = value
+            self.__changed = True
+            if self.__sync:
+                self.sync()
+
+    def __delitem__(self, key):
+        if key in self.data():
+            del self.__data[key]
+            self.__changed = True
+            if self.__sync:
+                self.sync()
+
+    def __getitem__(self, key):
+        return self.data(key)
+
+    def __iter__(self):
+        for key in self.data():
+            yield key
+
+    def __len__(self):
+        return len(self.data())
+
+    def __contains__(self, key):
+        return key in self.data()
+
+    def __str__(self):
+        return self.data().__str__()
+
+    def __del__(self):
+        self.close()
+
+
+def main():
+    """
+    test
+    """
+    LOG.basicConfig(level=LOG.DEBUG)
+    # LOG.debug('test log')
+    cache = Cache('test.txt')
+    cache['s'] = ['a', 's']
+    print cache
+    print cache['s']
+    print cache.time
+    cache['t'] = '哈哈'
+    print cache.time
+
+
+if __name__ == '__main__':
+    main()
diff --git a/ip.py b/util/ip.py
similarity index 100%
rename from ip.py
rename to util/ip.py