You should submit the following documents to Chinese embassy in Sri Lanka to apply for business visa:
1.A valid passport as well as a copy of its information page: Your valid passport must have at least six (6) months of remaining validity and at least one blank visa page in it.
2.Application form: One completed Visa Application Form.
3.Photo: one recent photo of 2x2 square inch (black & white or color is acceptable) glued or stapled on the application form.
4. Invitation letter from a company in China and a visa notification issued by authorized Chinese government departments, such as Committee of Commercial Relations with Foreign countries.

Reply to Bimal,
I am an Airline staff, been to China several times. My openoMy opinion is to write to Chinese embassy (mfa.gov.cn|chinaemb_lk ) in Sri Lanka, with all these your details and seek their advice and check whether they have a role in this. (Hope they will reply you)
On the other hand, this is the picture they have on Sri Lanka. We have to raise the Country.
Few years back, when I was traveling via Hong Kong, I was taken to a room from visa counter to check my docs as soon as they see my SriLankan passport. I inquired the reason later. That was due to lot of illegal involvements of SriLankan workers in Hong Kong. That is why they stopped issuing visa on arrival to SriLankans. It is a common responsibility of our people to protect our name.
China help Sri Lanka and friendship is there in the government level. But their filtering procedure on emigration is a different issue.

Normally in Sri Lanka, embassy ask for bank statements of several months from business visitors in addition to the docs mentioned by Mr Helper.

Upul Gunaratne
hotmail.com|upul_gunaratne