A method of reconfiguring an internet protocol (IP) address during handover by a mobile station (MS) is disclosed. In the method, the MS transmits a ranging request message to a base station (BS) in a network and then receives a ranging response message which includes a IP address refresh parameter from the BS in the network. Thereafter, the MS transmits an IP address configuration network entity search message via the BS, receives an IP address configuration network entity search result message from the network via the BS, and transmits an IP address configuration request message to the network via the BS. Lastly, the MS receives an IP address configuration response message from the network via the BS.