Disclosed is a direct current capacitor harmonic current suppression method. Back-to-back converters are adopted; the active direct current link capacitor current in the back-to-back converters is from superposition of direct currents of a rectifier i and an inverter i; the phases of harmonic components in the two currents i and iare determined by the relative phase PWM carrier waves of the rectifier and the inverter; and by actively controlling and regulating the frequencies and phases of PWM carrier waves in the rectifier and the inverter, the direct current link harmonic currents from the two converter levels can be the same in phases, so that the capacitor harmonic current minimization can be achieved. By adoption of the direct current capacitor harmonic current suppression method provided by the invention, harmonic contents and current amplitudes in the first and second carrier frequency bands in the direct current link capacitor current can be obviously lowered; and by virtue of the method, the power supply mass specification can be satisfied and capacitor current harmonic can be effectively reduced without using a high-capacity direct current link capacitor.