In the traditional PI speed control of permanent magnet synchronous motor (PMSM), there exists speed overshoot, large impulse current and poor anti-load-disturbance ability of speed loop. To solve these problems, a new variable structure PI (VSPI) control method based on the electromagnetic torque is proposed by deducing the mathematical model of PMSM and analyzing the PI control theory. On the basis of traditional PI control and VSPI control, the problems of speed overshoot and anti-disturbance are well solved by closed-loop control strategies such as fusing differential feedforward control and introducing torque feedback closed-loop control strategies. A voltage-current hybrid observation model and the corresponding calculation method are proposed for electromagnetic torque. Meanwhile, the influence of open-loop gain variation on system stability is analyzed in detail. Finally, the feasibility and effectiveness of the proposed method are verified by simulation.