please I want to apply for business visa to china,multiple entry visa,what are the requirement

You can't apply for China visa by post or internet. The requirements for business visa to Chian are:
(i) Original passport which has more than 12 months left before it expires from the date of application and sufficient blank visa pages.

(ii) One completed Visa Application Form with a recently-taken passport photo stuck on it;

(iii) An applicant who applies for a visa with multiple entries for the first time should provide an original Duly Authorized Unit or a Confirmation letter of Invitation issued by an Authorized Unit in China. If an applicant has been issued a visa with multiple entries before, he or she should provide an invitation letter from China and the copy of the previous visa with multiple entries.