A vector mode of one-cycle control for single-phase three-level APF is proposed, which can effectively reduce the switching losses by making one leg of single-phase APF work in a high-frequency switching state and the other work in frequency switching state. The working principle of single-phase APF is analyzed. Based on the fully considering of equalization control for the DC side capacitor voltage, five vector modes of one-cycle control for single-phase three-level APF are proposed and their control objectives equations are derived. Simulative results show that the five vector modes of one-cycle control are able to compensate the reactive and harmonic current effectively, which verifies its validity and feasibility.