diff --git a/README.md b/README.md
index a59aeeb..12cf839 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,11 @@ TODO
 
 ## 安装运行
 
+安装skepo.
+```
+yum install skopeo --nobest
+```
+
 
 运行同步程序
 
diff --git a/scripts/sync-to-jp.py b/scripts/sync-to-jp.py
index fca6e76..65d8282 100644
--- a/scripts/sync-to-jp.py
+++ b/scripts/sync-to-jp.py
@@ -1,5 +1,7 @@
 import os
+import json
 import random
+import subprocess
 
 REPO_REPLACE_RULE1 = {
     "k8s.gcr.io":"k8s-gcr-jp.m.daocloud.io"
@@ -23,40 +25,77 @@ INTERNAL_NETWORK = {
 
 
 REGISTRY_PASSWORD = os.environ["REGISTRY_PASSWORD"]
+DELTA_MODE = os.environ.get("DELTA_MODE") 
+DRY_RUN = os.environ.get("DRY_RUN")
 
+SKOPEO_CMD = "docker run --rm quay.io/containers/skopeo:latest"
+# SKOPEO_CMD = "skopeo" # RUN without docker
 
-SKEPO_CMD = "docker run --rm quay.io/containers/skopeo:latest"
-# SKEPO_CMD = "skepo" # RUN without docker
+def __run_cmd(cmd):
+    print(cmd)
+    if not DRY_RUN:
+        os.system(cmd)
 
-def skepo_sync_cmd(src_img):
-    src_img = src_img.strip()
-
-    dest_img = "/".join(src_img.split("/")[:-1])
+def __dest_img(src_img):
+    dest_img = src_img
     for k,v in REPO_REPLACE_RULE1.items():
         dest_img = dest_img.replace(k,v)
     for k,v in REPO_REPLACE_RULE2.items():
         dest_img = dest_img.replace(k,v)
     for k,v in INTERNAL_NETWORK.items():
         dest_img = dest_img.replace(k,v)
+    return dest_img
 
 
-    cmd = SKEPO_CMD + " sync --src docker --dest docker --dest-tls-verify=false --dest-creds root:%s -f oci %s %s" %(REGISTRY_PASSWORD,src_img,dest_img)
-#   print(src_img)
-#   print(dest_img)
-#   print(cmd)
-    return cmd
+def skepo_full_sync(src_img):
+    dest_img = __dest_img(src_img)
+    dest_img = "/".join(dest_img.split("/")[:-1])
+    cmd = SKOPEO_CMD + " sync --src docker --dest docker --dest-tls-verify=false --dest-creds root:%s -f oci %s %s" %(REGISTRY_PASSWORD,src_img,dest_img)
+    __run_cmd(cmd)
+
+def __parse_tag(output):
+    # print(output)
+    try:
+        return json.loads(output).get('Tags',[])
+    except:
+        return []
+
+def skepo_delta_sync(src_img):
+    dest_img = __dest_img(src_img)
+    cmd = "skopeo list-tags docker://" + src_img
+    result = subprocess.run(cmd, shell=True,stdout=subprocess.PIPE)
+    src_tags = __parse_tag(result.stdout)
+    cmd = "skopeo list-tags  --creds root:%s  --tls-verify=false docker://%s" %(REGISTRY_PASSWORD,dest_img)
+    # print(cmd)
+    result = subprocess.run(cmd, shell=True,stdout=subprocess.PIPE)
+    dest_tags = __parse_tag(result.stdout)
+    need_to_sync = set(src_tags) - set(dest_tags)
+
+    # print(src_img)
+    print("sync %s, src tag %s, dest tag %s " % (src_img,len(src_tags),len(dest_tags)))
+    # print(need_to_sync)
+    if len(need_to_sync) == 0:
+        if 'latest' in src_tags:
+            cmd = SKOPEO_CMD + " copy --dest-creds root:%s  --dest-tls-verify=false -f oci docker://%s:latest docker://%s:latest" %(REGISTRY_PASSWORD,src_img,dest_img)
+            __run_cmd(cmd)
+    else:
+        skepo_full_sync(src_img)
+
+    # print(src_tags)
 
 def main():
     lines = []
     with open("mirror.txt") as f:
         lines = f.readlines()
+    random.shuffle(lines)
     sync_cmds = []
     for l in lines:
-        sync_cmds.append(skepo_sync_cmd(l)) 
-    random.shuffle(sync_cmds)
-    for c in sync_cmds:
-        print(c)
-        os.system(c)
+        src_img = l.strip()
+        if DELTA_MODE:
+            skepo_delta_sync(src_img)
+        else:
+            skepo_full_sync(src_img)
+        
 
 if __name__ == "__main__":
     # execute only if run as a script