The invention provides an encryption protection system and method for a terminal device. The method comprises the steps that a network device obtains SIM encryption sequence information of a to-be-authenticated terminal device when a register application of the to-be-authenticated terminal device is received, and judges whether the obtained SIM encryption sequence information is stored in a memory or not; the network device sends the SIM encryption sequence information to an authentication server and obtains GPS information corresponding to the SIM encryption sequence information from the authentication server if the SIM encryption sequence information is stored in the memory; the current GPS information of the terminal device is compared with the GPS information returned by the authentication server; and the terminal device is accessed to a network if the information is the same. The SIM card information and GPS information of the terminal device are combined; the protection mechanism of the terminal device is enhanced; and the information loss resulting from the possible condition that terminal device is stolen, or the SIM card is copied and transplanted can be prevented.