An improved sliding mode observer is designed for the realization of the position sensorless control of the interior permanent magnet synchronous motor. The sliding mode observer is established based on the equivalent back electromotive force, with the saturation function adopted to replace the traditional switching function, which effectively improves the chattering problem of the observer output. The single-phase phase-locked loop is used to replace the traditional phase-locked loop to calculate the rotor position information, thus omitting the low-pass filter and phase compensation. Meanwhile, the differential operation is replaced by the forward differential transformation method, thereby reducing the calculation noise. The sliding mode speed controller is used to replace the traditional PI control so as to improve the anti-interference ability of the system. The simulation results show that the proposedmethod helps to eliminate the chattering, reduce overshoot and accelerate the response speed of the system.