The magnetic field modulation permanent magnet motor (MFM-PMM) achieves low speed and high torque output through the field modulation effect and has a significant advantage in term of high torque density. This paper introduces the working principle of this type of motor, designs the initial electromagnetic scheme based on the design parameters, and studies the impact of the speed ratio on the motor operational performance based on the initial electromagnetic scheme. The maximum torque, no-load back EMF and torque ripple characteristics of the motor at different speed ratios are simulated and analyzed, and the conclusion is drawn that the speed ratio is generally selected as a non-integer between 7 and 14. The speed ratio of this scheme is determined. A comparative analysis was conducted between the initial scheme and the optimized scheme to evaluate their respective performance. The comparison results show that, compared with the initial scheme, the maximum torque of the optimized scheme remains basically unchanged, the axial dimension is minished by 18.9%, the torque ripple is minished by 76.1%, the loss is minished by 53.1%, the efficiency is magnified by 3.5%, and the power factor is magnified by 1.4%. This research provides substantial theoretical guidance for the MFM-PMM design.