A method for unlocking a subscriber identity module, SIM, card, the method comprising: detecting (S100) and determining, by a mobile terminal, whether a currently inserted SIM card belongs to a preset SIM card in compliance with a specific operator; controlling (S200) the mobile terminal to access a network normally if yes; detecting (S200) lock information of an international mobile subscriber identity, IMSI, corresponding to the currently inserted SIM card if no; limiting (S300) the currently inserted SIM card to access the network when the lock information of the IMSI exists and a lock type of the IMSI is a lock state; the method characterized by further comprising: controlling (S300) the mobile terminal to access the network normally when the lock information of the IMSI exists and the lock type of the IMSI is an unlock state; initiating (S400) a function for locking the IMSI to generate a corresponding unlock code according to an international mobile equipment identity, IMEI, of the mobile terminal and the IMSI of the currently inserted SIM card when the lock information of the IMSI does not exist; and reminding (S500) a user to input the corresponding unlock code to control the mobile terminal to access the network normally when the mobile terminal detects that the currently inserted SIM card is locked. detecting (S100) and determining, by a mobile terminal, whether a currently inserted SIM card belongs to a preset SIM card in compliance with a specific operator; controlling (S200) the mobile terminal to access a network normally if yes; detecting (S200) lock information of an international mobile subscriber identity, IMSI, corresponding to the currently inserted SIM card if no; limiting (S300) the currently inserted SIM card to access the network when the lock information of the IMSI exists and a lock type of the IMSI is a lock state; the method characterized by further comprising: controlling (S300) the mobile terminal to access the network normally when the lock information of the IMSI exists and the lock type of the IMSI is an unlock state; initiating (S400) a function for locking the IMSI to generate a corresponding unlock code according to an international mobile equipment identity, IMEI, of the mobile terminal and the IMSI of the currently inserted SIM card when the lock information of the IMSI does not exist; and reminding (S500) a user to input the corresponding unlock code to control the mobile terminal to access the network normally when the mobile terminal detects that the currently inserted SIM card is locked. controlling (S300) the mobile terminal to access the network normally when the lock information of the IMSI exists and the lock type of the IMSI is an unlock state; initiating (S400) a function for locking the IMSI to generate a corresponding unlock code according to an international mobile equipment identity, IMEI, of the mobile terminal and the IMSI of the currently inserted SIM card when the lock information of the IMSI does not exist; and reminding (S500) a user to input the corresponding unlock code to control the mobile terminal to access the network normally when the mobile terminal detects that the currently inserted SIM card is locked. <EOS>