my double entree visa will expire in 12days. I want to apply for a.new.one at PSB.

Milan, you can visit local entry and exit management bureau to ask for the extension. You need to bring your passport, filled application form, a recent passport photo, temporary accommodation registration form, hotel booking, travel itineraries and return air ticket. In addition, you might be required to provide a Chinese bank account that has CNY 21000 at least.