A visa, affixed to your passport, is required to visit China. Registrants are responsible for obtaining their own visas. There are a number of agencies that provide visa services. One is the USA branch of China International Travel Service (CITS). CITS is authorized by Chinese Consulate General to handle China visas for travelers across the USA.
http://www.citsusa.com/visa.htm

CITS USA, Inc.
975 E. Green Street, Suite 101
Pasadena, CA 91106
Questions can be directed to CITS USA, 626-568-8993, fax 626-568-9207
E-mail: info@citsusa.com
http://www.citsusa.com