The requirements for L visa for family visiting are: (theinviter is your Chinese wife)
(I) Original passport with validity more than six months and minimum 2 blank visa pages;

(II) Photocopy of the first 2 pages (personal information) of the passport and the recent Chinese visa page if there is any;

(II) One fully completed visa application form in Chinese or English, attached with one of the applicant's recent color photograph (30mm X 40mm)

(III) Certificate of the relationship between you and the person in China you want to visit (original and photocopy)

(IV) Invitation letter from your wife you want to visit

(V) ID card copy of your wife

Generally speaking, if you apply for L visa for the first time, it permits you to stay in China for 30 days, you can extend the stay duration of visa for 2 times at most.