I think, you need a business visa to China for your trade purpose, the requirements for a business visa are as follows:
1. A fully filled application form.
2. Applicant's passport valid for at least six months with at least 2 blank visa pages and its photocopy.
3. One recent passport size photograph.
4. A letter of invitation from China
5. Covering letter from applicant's company or employer addressed to the visa office.