You can apply for Hong Kong visit visa through Beijing Office of Hong Kong Immigration Department:
Address: 71, Di'anmen Xidajie, Xicheng District, Beijing 100009)
Tel: (8610) 6657 2880
Fax (8610) 6657 2821
E-mail address: bjo-hksarg.org.cn|bjohksar

It takes about one week if you apply for single entry Hong Kong visa with 14 days stay duration, otherwise, it takes as long as 1 month because the application will be sent to the immigration office of Hong Kong.

The requirements are your passport, one passport photo, one filled Hong Kong visa application, round-trip flight tickets or other transportation arrangement, the copy of your multiple-entry student visa.