Permanent magnet synchronous motors typically employ PWM (Pulse Width Modulation) for precise control of speed and torque to meet diverse industrial application requirements. However, in high-speed, high-power permanent magnet motor applications, limitations in switching losses and cooling conditions often restrict the inverter switching frequency to below 1 kHz. This results in a relatively low carrier frequency when PWM is applied to the inverter, leading to load current distortion and increased motor torque ripple. To address these issues, this paper establishes a rotor current model for permanent magnet motors based on the switching angle sequence of a three-phase three-level inverter, considering the harmonic and torque characteristics of permanent magnet synchronous motors. It proposes a multi-objective optimization modulation technique based on current harmonics and torque ripple, solving it via a multi-objective genetic algorithm. This yields a modulation strategy for permanent magnet motors that minimizes the impact of current harmonics and torque ripple, providing a new approach for optimizing modulation in high-speed, high-power permanent magnet motors operating under low carrier ratio conditions.