The number of action devices is currently increasing. If the trade environments are not safe, both the development and the progress of electronic trade will be affected. As well as security issues, the handoff procedure incurs long latency and packet loss. Smooth handoff can not only lower the packet loss but also reduce the level of the out-of-sequence packets. So far, very little attention has been given to the Internet key exchange for encryption in mobile network. This study examines Internet key exchange in smooth handoff for mobile IPv6 network and compares the proposed method with the classic smooth handoff technologies. It shows that the proposed solution is more efficient in mobile IPv6 networks