The rotor step skewing can effectively reduce the torque ripple of the permanent magnet synchronous motor (PMSM), but it will decrease the average output torque of the motor. In order to solve this problem, the magnetic isolation bridge is optimized on the basis of the rotor step skewing to improve the average output torque. Firstly, the influence of the rotor step skewing on the cogging torque, no-load back electromotive force (EMF), torque ripple and average output torque of the motor is analyzed, and the optimal number of rotor segments and step skewing angle are selected. The segments is 3, the step skewing angle is 5°, the torque ripple keeps unchanged. Under these conditions, the optimal magnetic isolation bridge structure is found by optimizing the rotor parameters HRib and Dmin, and the average output torque increases from 138.5 N·m to 147.2 N·m. The effectiveness of the method is verified. Meanwhile, the peak value of cogging torque decreases from 0.24 N·m to 0.18 N·m, the amplitude of no-load back EMF fundamental wave increases from 278.7 V to 288.6 V, and the harmonic distortion rate is nearly unchanged. The results indicate that other performances of the motor can be improved after optimization of the magnetic isolation bridge.