The traditional sliding mode observer method is used to obtain the rotor position in the position sensor control of the permanent magnet synchronous motor. The accuracy of rotor position estimation is affected by the factors such as the serious vibration of the sliding mode, the low harmonic interference contained in the estimated reverse potential and the position error of the conventional phase-locked loop when the motor is reversed. The above problems are solved by designing an adaptive sliding mode observer and improving the phase-locked loop. Firstly, a non-singular fast terminal sliding mode surface and an improved exponential approach law are adopted to reduce the sliding mode vibration. Secondly, the traditional phase-locked loop phase detector is improved and the second-order generalized integrator is introduced into the loop filter, which not only enables the accurate extraction of rotor position information when the motor is rotating forward and reversed, but also can filter out the low harmonics in the estimated reverse potential. The simulation results show that the effectiveness of the designed algorithm in reducing the sliding mode vibration, decreasing the delay time of position tracking, and improving the accuracy of position observation.