A communication device and a starting up method include determining if the communication device has been locked with a designated subscriber identification module (SIM) card, and determining if an acquired unique International Mobile Subscriber Identity (IMSI) code of a current SIM card matches a prestored IMSI code of the designated SIM card when the communication device has been locked with a designated SIM card. The communication device and method further include unlocking the designated SIM card with the communication device if the acquired IMSI code does not match the prestored IMSI code, and starting up the communication device.