My wife is Chinese citizen, and I need to visit her I have wedding documents and her Id (citizen card details) so how do I apply for visa?

Applying Tourist Visa for Visiting Families, the following documents are required:

(1) Covering letter from your company or office.
(2) marriage certificate, copy of her ID card
(3) Invitation letter from your Chinese wife.
(4) Comfirmed return flight ticket and its photocopy.
(5) Photocopy of the personal data page of your passport.
(6) filled visa application form V.2011A

If you want to get a China visa in New Delhi or Mumbai, you need to submit application to China Visa Application Service Center in New Delhi or Mumbai.