In this article, based on flux modulation theory, torque characteristics improvement method is proposed for double-stator vernier permanent magnet (DS-VPM) motor. Also, the detailed torque production mechanism of DS-VPM motor is derived. Based on theoretical analysis results, key design parameters which possess significant influence on motor torque characteristics are selected to be further optimized purposefully. Non-dominated sorting genetic algorithm is then adopted to obtain increased output torque and reduced torque ripple of inner, outer, and total DS-VPM motor. Besides, based on finite-element analysis, motor performances before and after optimization are compared in detail. Finally, a prototype motor is built and corresponding experiments are carried out. Both theoretical analysis and experimental results verify the effectiveness of the proposed torque characteristics improvement method, which provides a potential research path for the design optimization of high-performance VPM motors.