A method for Access Authentication in the High Rate Packet Data Network is proposed in the present invention comprising steps of the AN-AAA receiving the Radius Access Request message sent from the HRPD AN; the AN-AAA judging whether a terminal is a roaming one according to the Network Access ID and transmits the roaming terminal's authentication information to the terminal's home nerwork. If said terminal is a local one, the AN-AAA judges the type of the terminal according to the NAI value. If said terminal is a single-mode one, the AN-AAA works out the Result2 with the MD5 algorithm. if said terminal is in dual-mode, the AN-AAA calculates the Result2 with the CAVE algorithm to compare the Result1 with the Result2.