The invention relates to a control method of a power supply for capacitor ripple test. The method comprises the steps of determining required sampling periodic number at different frequencies by a preset sampling strategy, and calculating a feedback value of an output current effective value; calculating deviation between the feedback value of the output current effective value and a given value of the output current effective value, and adjusting and outputting a second bus voltage according to the deviation; and calculating each IGBT switch-on condition according to a given output current frequency and the given value of the output current effective value so as to obtain a PWM wave of a frequency modulation circuit, and controlling to output an output current matched with a test given value. By the method, high-frequency, high-accuracy and large-current output of the power supply for capacitor ripple test can be achieved.