A Dynamic Host Configuration Protocol (DHCP) authentication method includes: authenticating a Routing Gateway (RG) by an Authentication Server (AS) that serves the RG; receiving an access policy from a DHCP authenticator after the RG passes the authentication; and starting DHCP authentication according to the access policy, and performing DHCP authentication for a DHCP client connected to the RG. With the present invention, the DHCP authentication is started on the RG, and the DHCP authentication is performed for the DHCP client connected to the RG. Therefore, the DHCP client connected to the RG can undergo DHCP authentication through the RG to access the network.