Method and system of registering mobile node in mobile IP environment

A method of registering a mobile node on a home agent in a mobile IP environment and a mobile IP network system using the same are provided. The method of registering a mobile node on a home agent in a mobile IP environment includes: collecting care-of-addresses of foreign agents of subnets adjacent to a first subnet in which the mobile node currently resides; broadcasting messages containing the collected care-of-addresses when the mobile node moves from the first subnet to a second subnet adjacent to the first subnet; in the foreign agent of the second subnet, receiving the broadcast messages and extracting the care-of-addresses; and in the foreign agent of the second subnet, transmitting the extracted care-of-address to a home agent of the mobile node to register the mobile node on the home agent if one of the extracted care-of-addresses is identical to the care-of-address allocated by the foreign agent of the second subnet.