A method and device for acquiring a rotor position based on a permanent magnet synchronous drive system. The permanent magnet synchronous drive system includes an inverter and a permanent magnet synchronous motor, wherein the initial speed of the permanent magnet synchronous motor is not zero. The method includes: controlling a bridge arm switch of an inverter periodically; collecting a three-phase current of the permanent magnet synchronous motor at a fixed time within each control period; and after the three-phase current is reversed, sending same to a phase-locked loop system to conduct processing, so as to obtain a phase angle of an induction potential vector, and according to the phase angle of the induction potential vector, acquiring a rotor position angle of the permanent magnet synchronous motor.