In this paper we challenge the user Authentication using Kerberos V5 authentication protocol in WPKI environment. this paper is the security structure that defined in a WAP forum and security and watches all kinds of password related technology related to the existing authentication system. It looks up weakness point on security with a p개blem on the design that uses wireless public key-based structur and transmission hierarchical security back of a WAP forum, and a server-client holds for user authentication of an application level all and all, and it provides one counterproposal. Therefore, We offer authentication way solution that connected X.509 V3 with using WIM for complement an authentication protocol Kerberos V5 and its disadvantages.