Access authentication is very important for mobile IPv6 networks. In this paper, hierarchical access authentication method in mobile IPv6 (HAMIPv6) is proposed. The method can accomplish access authentication and mobile registration while reducing exchanges between mobile node and home domain by utilizing authentication vector and message piggyback. The method simplifies handoff authentication process by reducing handoff delay and cost. Also the method supports mutual authentication between terminal and network. Performance evaluation shows that the proposed method is better than the others, especially in the conditions that MN is far from home domain and move frequently within a domain.