An authentication method and device. The method comprises: when receiving a first HTTP access request message carrying login information and sent by a target user terminal, sending a second HTTP access request message carrying an IP address of the target user terminal to a target Portal/AAA server deployed in a target subnetwork where the target user terminal is located; When receiving the first HTTP authentication response message returned by the target Portal/AAA server, sending the authentication result carried in the first HTTP authentication response message to the target user terminal through the second HTTP authentication response message. The application of the embodiment of the invention can ensure the compatibility of the authentication scheme on the premise of improving the safety of the network.