The present invention provides a method, a device and a system for locking card in the mobile terminal, wherein, the method includes that: when a mobile terminal is powered on and started, it is detected whether the starting condition is satisfied according to the locked data in the software dog; if so, then the mobile terminal is started normally; if not, the mobile terminal is failed to start. The present invention adopts a software dog to store the locked data, overcomes the defect in the related art that the locked data stored in the mobile terminal is easy to be overwritten and erased, and solves the problem that a potential security hazard is existed in the mobile terminal locking (U) Subscriber Identity Module (SIM) card, thus complying with the original intention of the mobile terminal locking card service, and better protecting the interest of the operator.