Aiming at the problem of torque ripple caused by cogging torque in the external rotor permanent magnet synchronous motor, this study proposes a method for reducing the cogging torque by the eccentric structure of stator teeth. Taking a 3 kW external rotor permanent magnet synchronous motor as an example, the validity of the method proposed is verified by theoretical analysis and finite element calculation. Finally, the other performances of the models with different teeth eccentricities are compared, and a prototype is manufactured to verify the correctness of the simulation results. The research shows that the eccentric structure of stator teeth does not affect the other performances of the motor greatly while reducing the cogging torque of external rotor permanent magnet synchronous motor effectively.