A method and system for accessing a cellular mobile communication network, the method includes: after a terminal and a base station complete a ranging process, the terminal carrying out a basic capability negotiation with the base station, the base station and the terminal carrying out a WAPI access authentication process; and the terminal carrying out a subsequent access flow to access the cellular mobile communication network; wherein the WAPI access authentication process includes: the terminal sending an access authentication request packet, including a certificate and a signature of the terminal, to the base station; the base station authenticating the signature of the terminal, including the certificate into a certificate authentication request packet to send to an authentication server to perform validation; the base station sending an access authentication response packet to the terminal, and carrying out a unicast session key negotiation with the terminal to obtain a unicast session key.