Inspired by V-shaped permanent-magnet machines and the method of tooth notching, a rotor auxiliary teeth field-modulated permanent-magnet motor (RAT-FMPMM) is proposed to improve the torque performance of FMPMM. Firstly, the structure of the RAT-FMPMM is introduced, and then the working principle is analyzed. Secondly, the electromagnetic performance of the proposed motor, such as air gap flux density, cogging torque, back-electromotive force (Back-EMF), inductance and output torque, are analyzed by 2D finite element method (FEM). In addition, it is compared with a FMPMM whose rotor has no auxiliary teeth (RWAT-FMPMM). The comparative results show that the introduction of auxiliary teeth can significantly increase the magnetic field of the armature currents, thereby increasing the torque, but it will also cause large torque ripple. Finally, to further improve the torque and reduce the torque ripple, the key design parameters of the proposed motor are optimized by multi-objective optimization. The optimization results show that the torque ripple is reduced by 25%, and the output torque is increased by about 17.6%.