If the invitation letter from Canton fair doesn't prescribe multiple entries, you can't get a one year multiple-entry visa, the required documents for China Business Visa Application are:
1. A completed visa application form
2. Original passport and a passport copy (A-4 size).
3. A copy (A-4 size) of the U.A.E. residence visa, which usually should be valid for more than 6 months, if the applicant is non-U.A.E. national.
4. A photograph as in the passport.
5. a copy of the trade license, if self-employed.
6. An invitation letter from Canton fair
7. A copy of the round air ticket, confirmed hotel reservation and personal bank statement, if required by the consular officers.