Provided are a super peer based P2P network system and a peer authentication method thereof. The authentication method includes a first authentication process and a second authentication process. In the first authentication process, a user and a peer which want to use a P2P network are verified by submitting authentication information and a public key infrastructure (PKI) certificate, and receive the permission of connection. In the second authentication process, a user and a peer requesting the use of a specific service are authenticated by using an authentication ticket and a service access-permitted time is limited in order to reinforcing the security of the specific service, which is searched in the P2P network and provided by the peer. Accordingly, the service providers can verify users more securely and limit the service available time of each user with respect to a specific service provided by the peer by using the lifetime of the ticket.