In this paper, an analysis for a single-phase active power filter (APF) based on one cycle control (OCC) is presented. The control method eliminates the need of sensing the load current, a nontrivial task of calculating the harmonics and reactive current components, as well as the use of multipliers, as reported by many previous reported control methods. In addition, the phenomenon of DC offset is discussed. In order to improve the problem, a modified control strategy is proposed. In contrast to previously proposed control strategy used for APF based on OCC, the new one can effectively suppress the DC offset and the cross distortion. Therefore, the key problems of APF based on OCC are solved. The theoretical analysis is verified by simulation.