Different system switching method for double-module double-standby terminal

The present invention discloses the different-system switching method of a dual-mode dual-standby terminal. When the signal quality of a 3G network is lower than a pre-set threshold according to the judgment of the 3G module in the dual-mode dual-standby terminal, the 3G module informs the 2G module in the dual-mode dual-standby terminal; and the 2G module sends a special call request message to the network side entity of the 2G module. The network side entity of the 2G network receives the special call request message and directly distributes the network resource of the 2G network to the dual-mode dual-standby terminal and processes the corresponding follow-up switching processing. The present invention can smoothly switch the processing communication to the 2G network when the dual-modedual-standby terminal is located at the place where the covering signal of the 3G network is not good.