Abstract: To improve the performance of speed controllers for permanent magnet synchronous motors, a new varying speed reaching law sliding mode control strategy is proposed. The varying speed reaching law introduces a power term on the system state and a variable speed term on the sliding mode function based on the traditional exponential reaching law, and uses a hyperbolic tangent function to reduce the effect of the high-frequency switching term. This control strategy helps to reduce current and torque pulsations and improves the stability and responsiveness of the system operation. In addition, to address the problem that the system is affected by unknown disturbances, a sliding mode disturbance observer is designed to estimate the total disturbance of the system, and the estimated disturbance is compensated into the composite speed controller. Finally, the proposed control strategy is verified by using Matlab/Simulation simulation and motor experimental platform. The simulation and experimental results show that the control strategy combining the composite speed controller with the disturbance observer has faster convergence speed, less chattering, and better anti-disturbance performance.