In order to ensure the orientation accuracy of rotor flux, a method of online correction of rotor flux linkage angle was proposed. By measuring the variation of phase current during zero voltage vector in space voltage vector PWM, the accurate angle of rotor flux could be calculated. The regulator adjusts the frequency of the slip angle online to correct the rotor flux angle so as to improve the motor control performance. The correctness of the theory and the validity of the method were verified through experiments.