I am a Singaporean and if I need to stay in Chian for business for one month, how long would a visa takes and what documents do I need to present for the application?

yes, you need business visa to visit China for one month, you don't need a visa to visit China fror 15 days. The requirements for business visa:
1. One completely filled out visa application form. No item should be blank .
2. One recently taken 2X2 in. photo showing entire face and without a hat on. Please affix the photo to the application form.
3. Original passport with at least 2 blank visa pages and valid for at least 6 months beyond the date of application.
4. Visa conformation letter from an economic and trade bureau or a foreign affairs office of the provincial or municipal government.

it takes 4 working days for visa processing.