A mobility supporting method and a mobility supporting system using the method are provided. The mobility supporting method includes a first access router for allocating a prefix to a mobile terminal, and registering the allocated prefix in an authentication server when the mobile terminal connects to the first access router. There is also the authentication server for verifying the mobile terminal based on the registered prefix, and reporting a result of the verifying of the mobile terminal to a second access router when the mobile terminal moves to connect to the second access router and the second access router for notifying the reported result of the verifying the mobile terminal to the first access router.