A method and system for implementing DHCP address security allocation and authentication server. The core of the invention is that DHCP client end send the discovery message through access network; when the access network side acquires the identification information such as the port information of said DHCP client end and the like and authenticates it based on said identification information; finally DHCP server only allocates the address information for the authorized DHCP client end. Therefore the invention may perform accessing authentication for user according to the location information and only allocates the address for the legal user terminals thereby it enhances the security for allocating address through DHCP manner. Also in the invention the address is managed unifiable by the AAA server or allocates the address after the AAA server authenticates successfully.