You need further prepare following documents:
1. Original passport and a photocopy of its pages with personal information.
2. A fully completed Visa Application Form with your signature.
3. An original letter from your employer. It should contain your name, nationality, occupation, purpose of the visit, the planned date of entry and financial conditions.
4. A passport photo with white background.
5. A photocopy of a valid residence permit in Saudi Arabia.

Dear Mr. Alvin,
Thanks for your prompt reply, however i went to Riyadh with all five below mentioned document and Al Sandross Chinese Visa Application services centre refuse to accept my application and said that i need to bring invitation letter from our supplier in China that should be attested by foriegn office in China, now our supplier confirms that it will took them ten days to do so, i need to attend Goungzhou Office Furniture exhibition starting 26. Now i plan to go to Islamabad to get visa. Please advise further, thanks again
OMER

Oh, maybe you can try to apply for a tourist visa using their rush service for processing. If you do not want to go there in person (in case of they remember you), application can be submitted by someone entrusted.