I am Pakistani passport holder working in China and have (residency permit for foreigner).

Umer, you can apply for it from China. You have at least 50% chance to get it.
If you want to apply for a tourist entry permit for USA, you need to provide those documents containing your passport, a passport-style photo, proof of your financial support, travel itinerary, non-criminal certificate, your residence permit in PRC and other documents required by the consular officers. It will take 3 working days to process your application.