The utility model discloses a protective device of a self-lifting platform-lifting system. The protective device comprises a man-machine operation unit, a numerical control unit and a first data acquisition unit, wherein the first data acquisition unit collects the current of a lifting motor and transmits the current signal to the man-machine operation unit for displaying. When the abnormal condition occurs, the man-machine operation unit sends a control command to the digital control unit, and the digital control unit, according to the control command, drives an execution unit to control the operation of the lifting motor. The protective device can not only protect the motor against overload in a real-time manner, but also facilitate the dynamical monitor for the operation of the platform-lifting system, can give the alarm for the hazardous operations, and can automatically shut down the relevant devices at the critical moment to prevent the further failure propagation.