In an antitheft method for a mobile terminal that relates to the field of communications technologies, a baseband processor detects integrity of an operating system running on an application processor, generates a short message service (SMS) message when the operating system has no integrity, and transfers the SMS message to the application processor. The application processor controls a display to display the SMS message in order to inform a user that the operating system of the mobile terminal is damaged. In a scenario in which a mobile terminal is stolen and an operating system is maliciously tampered with, according to the solution provided in this application, an SMS message is used to prompt a user, thereby improving security of the mobile terminal.