Provided are a mobile network system capable of processing a high-speed handoff by dividing into a data packet path between mobile nodes and a handoff packet path of the mobile node, and a method for processing IP handoff thereof. The system includes a MAP broadcasting a handoff registration request and reply between a foreign agent and a home agent, and an additional handoff signal path between the MAP and a mobile agent operating as a foreign agent and a home agent by means of a HAAP and VPN technology to be physically distinguishable from a data path. Therefore, limitation in a head of line can be resolved and the IP handoff can be promptly provided.