Do you have a business partner in China who can help you to apply for China visa? If not, you can't apply for Business Visa to China
the required documents for Business Visa are:
A. One completed visa application form;
B. One recent passport sized photo;
c. original passport with blank visa pages and at least 6 months validity
D. An invitation letter/fax from your contact in China
E. an invitation letter from a Chinese governmental department
F. round-trip flight tickets and hotel reservation.

Now, Sri Lanka passport holders can't apply for individual tourist visa, you have to join a tour, please contact a travel agency and deal with all issued, then it can issue you a group visa notice or apply for a group visa for you.