[Objective] To address the cogging torque suppression issue in axial flux permanent magnet synchronous motor (AFPMSM), this paper proposes an optimal design method based on an asymmetric slot depth structure, aiming to significantly suppress cogging torque and thus improve the operational stability and reliability of the motor. [Methods] Firstly, an analytical calculation model of cogging torque was established based on the energy method, and the general method for cogging torque suppression was theoretically derived. Then, taking a 20-pole 18-slot AFPMSM as the research object, a finite element simulation model was constructed, and a regulation method for the height dislocation difference of stator slot depth was proposed. By adjusting the height difference of adjacent stator teeth Δh, the variation laws of Δh on the harmonic distribution of air-gap magnetic flux density and cogging torque were systematically analyzed. Finally, the effectiveness and engineering feasibility of the proposed optimal design method were verified through simulation. [Results] The simulation results showed that on the premise that the slot fill factor met the working condition requirements, compared with the conventional AFPMSM, the asymmetric slot depth structure achieved the optimal cogging torque suppression effect when Δh=0.6 mm, with a suppression rate of 79.18%. [Conclusion] This paper verifies the effectiveness and feasibility of the asymmetric slot depth structure for cogging torque suppression, reduces the torque ripple by means of this structure, and thus provides a technical approach and reference for the electromagnetic optimal design of AFPMSM.