Aiming at access security aspect of 3G-WLAN heterogeneous wireless network, this paper abstracts each entities of heterogeneous wireless network, thereby establishes a general authentication model. Then based on this general authentication model, a novel access authentication and key agreement scheme by using Canetti-Krawczyk (CK) model is devised. This scheme simplifies the authentication process and information between access network server and home network server by using Public Key Infrastructure (PKI) to distribute public key. It also decreases the authentication computational complexity of mobile terminal by Elliptic Curves Cryptography (ECC). Finally, formal analysis and proof with CK model for the proposed protocol are given. It is showed that the proposed scheme is secure and efficient.