The present invention relates to a method of performing handover from an asynchronous mobile communication network to a synchronous mobile communication network. If the access network of the asynchronous mobile communication network (100) requests handover to an MSC (104) of the asynchronous mobile communication network, the MSC requests/receives subscriber information of the mobile communication terminal from a dual-stack HLR (300), and transmits a handover request message to the synchronous mobile communication network (200). The MSC (203) of the synchronous mobile communication network assigns a forward channel to the mobile communication terminal. The asynchronous mobile communication network (100) transmits a handover instruction message to the asynchronous RF device of the mobile communication terminal. Accordingly, the mobile communication terminal sets up a synchronous RF device, connects to the synchronous mobile communication network through reverse channel assignment and synchronization. The mobile communication terminal transmits a handover completion message to the synchronous mobile communication network.