Some more background.

“The Sino-foreign couple must go together, in person to the appropriate marriage registration office and submit a completed marriage registration application form (available at the marriage registration office). The appropriate marriage registration office will be the one in the jurisdiction in which the Chinese partner is registered (the location of the hukou).

Together with the application form, the couple must submit a number of other documents: http://www.china.org.cn/english/LivinginChina/184441.htm

Chinese Partner

(1) A certificate of marriageability
(2) A certificate of birth
(3) Household registration book (hukou)
(4) A health certificate (obtainable from a regional-level local hospital)
(5) A letter from the parents of the Chinese partner giving permission for their child to marry a foreigner (this letter should include the index fingerprint of both parents below their signatures and date)

Foreign Partner

(6) A current passport
(7) Chinese residence permit
(8) A health certificate from a local hospital designated by the marriage registration office
(9) Three photos of the marrying couple, taken together
(10) A registration fee
(11) A certificate of marriageability.

Item 11 requires further explanation. Basically, the marriage registration office needs a form from the foreign partner's home government stating he/she is not already married in his/her home country. Every foreign government has its own version of this type of form with its own requirements for obtaining one. Couples will need to check the embassy website of the foreign partner's home country in China for details on how to obtain this kind of certification. (Chinese translations must accompany foreign-language documents.)

Note: Application requirements may vary from office to office.”