回複：回複：回複：請問 863211 一個問題

Yes, you can change your I-485 to consular processing (CP). You must file Form I-824, Application for Action on Approved Petition, after the I-140 is approved. This notifies the USCIS to transfer the file to the consulate. Before you egt the interview for your immigration visa in China, you need to get a permanent job offer from a US employer.

I can not discuss it with you in details here. You can find a lot of information in internet, here are some websites:
http://www.immihelp.com/greencard/adjustment-of-status-vs-consular-processing.html

http://www.immihelp.com/gc/consular/ac140.html