In the position sensorless control method in low-speed region of the fault-tolerant permanent magnet motor system based on the envelope detection and the non-orthogonal phase-locked loop of the present disclosure, the position sensorless control of the motor is implemented by injecting the high-frequency voltage signals into any two non-faulty phase windings of the motor, extracting the high-frequency response currents of the high-frequency injected phases by the digital bandpass filter, calculating the differential mode inductances of the two phase windings through the envelope detecting and signal processing, and extracting the rotor position and rotational speed signals from the estimated two phase inductances through the non-orthogonal phase-locked loop. In addition, the controller of the present disclosure is small in size, high in accuracy, and high in reliability, which can effectively meet the performance requirements of the onboard electric actuators.