Compared with traditional permanent magnet synchronous machines (PMSM), the Interior Permanent Magnet Synchronous Machine with Unequal Tooth Widths (UNETIPMSM) offers advantages such as high torque density and good fault tolerance. However, this also leads to an increase in torque ripple. To suppress the torque ripple of UNETIPMSM, a method of stator/rotor auxiliary slots was studied. The mechanism of torque ripple generation in permanent magnet synchronous motors was analyzed. A finite model of a 10-pole/12-slot motor is established to perform electromagnetic simulation. Three types of auxiliary slots are proposed, with notching the armature tooth, fault-tolerant tooth, and both the armature and fault-tolerant tooth. Additionally, the effects of the slot width and depth of rotor auxiliary slots on torque ripple are investigated, and three auxiliary slot structures are compared. The results indicate that appropriately designed auxiliary slots on the stator and rotor can effectively reduce torque ripple while maintaining the motor’s performance.