The invention discloses a d-axis positive direction determination method of a permanent magnet synchronous motor, comprising the steps that firstly a pulsating high frequency current injecting methodis adopted to establish a rotor closed loop system, and the d-axis voltage response is obtained; secondly, the amplitudes of the d-axis voltage response (1) are recorded when the injection current signal phase is pai / 2, 3pai / 2; the value of the two amplitudes are compared, and the d-axis positive direction is determined, and the compensation value of the d-axis positive direction after determination can be obtained. The rotor synchronization rotating coordinates q-axis current can be set as 0, and the d-axis current is injected with a pulsating high frequency sinusoidal signal, and the rotor closed loop system can be established, and the d-axis voltage response of the rotor synchronization rotating coordinates can be extracted. The invention is advantageous in that during the process of determining the d-shaft positive direction, the injected current is always the sine high frequency signal, and signals of other types like positive and negative pulse are not required to be injected, and estimation process can be simplified; motor running cannot be affected; the structure is simple, reliability is high, operation complexity can be reduced, and the process of estimating the initial position can be simplified.