When I post an new post, I can see the address status bar showing "connecting to twitter.com...." as below
 5.jpg You have insufficient rights to see the content.

But Twitter is not accessable in China, How can I remove anything relate twitter/facebook/google etc? China goverment blocks them. That cause long time for loading a page

You need to remove the Twitter BB Code Extension, that is loaded on the page you referring to..

Go to Admin > Settings > BBCode Extensions > And Delete the Twitter Extension.