Cogging torque is one of the important problems of permanent magnet motors. Weakening the cogging torque can reduce torque ripple, reduce electromagnetic noise, and improve motor stability. The cogging torque of the surface permanent magnet synchronous motor (SPMSM) is studied based on magnetic pole parameters. Based on the energy method and Fourier decomposition, the cogging torque formulas under different permanent magnet models are derived. It is found that the change of magnetic pole parameters affects the permanent magnet remanence distribution in the air gap and the relative permeability of the air gap, thereby changing the cogging torque. Then combined with the finite element method, the cogging torque of different permanent magnet models is simulated and analyzed. It is found that the polecut structure and combined magnetic poles significantly weaken the cogging torque. The magnetic pole parameters of these two structures are optimized by the finite element method. The influence of magnetic pole parameters on other performances of the motor is analyzed. The result shows that reasonable selection of permanent magnet parameters can significantly reduce cogging torque while ensuring motor performance.