Can I repair my iphone 4s in China bought in US

Any Apple Store should repair it

If you have an apple store near you, you can take it there. You might be able to get it done at your carriers store. Most likely though they'll tell you to send it to apple to get it fixed. So if you don't have an apple store near by, I think you'll have to send it to apple. Hopefully you're still under warranty, or have applecare.

you can call AppleCare or go to Apple Store, any iPhone is entitled for the available service in the coutry where they are located.

to book Apple Store Appointment go to: http://www.apple.com/retail/geniusbar/

or call hotline: (86) 4006-272273 or Start your support request online