Method for automatically switching numbers of SIM card

The invention discloses a method for automatically switching numbers of an SIM card, and relates to a method of an SIM card program function and a background to send number resources to the SIM card.The method comprises the following steps: pre-loading an SIM program, an SIM card smart tool kit and a main number in the SIM card, when the main number of the SIM card detects regional information change in the case of logging in the network, automatically sending, by the SIM card, information to a background server to switch an auxiliary number; and when the SIM card detects that the mobile phone exceeds the region supported by the auxiliary number or exceeds the valid time, automatically switching, by the SIM card, the main number. By adoption of the method disclosed by the invention, automatic number switching is achieved, in the case of logging in the network through the main number, by detecting MCC transition/time/card state, the auxiliary number is switched, the auxiliary number isalso elastically selected