This invention relates to an anti-cloning method for SIM card including the following steps: 1, a second SGSN responds to a coherence request of a second user to initiate a position refreshment request to HLR, 2, HLR judges if a first user having the same international mobile user ID with the second user has already adhered to the first SGSN, if not, HLR responds to the position refreshment request of the second SGSN, otherwise, it informs the first SGSN to knockout the first user, 3, the first SGSN responds to the HLR separation information to start a timer with the length longer than that of a systematic period route refresh timer, 4, the first SGSN knockouts the first user if it does not receive the report information of the first user in a period of time designed by the timer, or it informs the system the user is duplicated. |