An enterprise needs electronic commerce in Internet/Intranet environment whose security depends basically on User Identification. After studying on present identification methods and protocol, we present, in this paper, a mutual Strong User Identification system based on Kerberos protocol, public key cryptosystem, digital certificate and smart card. Several limitations of Kerberos protocal are overcome. This system satisfies the speed requirement of mutual real time identification. Moreover,it can simplify the actions of key management, distribution and storage, relieves the client's burden.