A method for accessing a 3G network includes: a terminal accessing a wireless local area network by adopting a WAPI protocol, and notifying an AAA server of a 3G network through an AP of the wireless local area network that the terminal intends to access the 3G network; the AAA server obtaining identity information of the terminal through the AP, and performing an EAP-TLS negotiation process with the terminal through the AP after determining that the terminal is a subscription terminal of the 3G network according to the identity information; and the terminal accessing the 3G network after finishing the EAP-TLS negotiation process. A system for accessing a 3G network includes an AP of a wireless local area network and an AAA server of a 3G network. The present invention reduces unnecessary processes the message interacting, the certificate verification, the signature verification, and so on and improves the system efficiency.