[求助]北京签证最多提前多少天？

Students should note that Embassies and Consulates are able to issue your student visa 120 days or less, in advance of the course of study registration date. If you apply for your visa more than 120 days prior to your start date or registration date as provided on the Form I-20, the Embassy or Consulate will hold your application until it is able to issue the visa. Consular officials will use that extra time to accomplish any of the necessary special clearances or other processes that may be required.

http://travel.state.gov/visa/temp/types/types_1268.html#apply