Abstract: The regular control based on the p-q theory and the one based on the DC-link voltage are two typical control schemes for parallel active power filter（PAPF）.Since the interrelationship between these two control schemes has not been deeply analyzed,this paper studied on the regular control mechanism of PAPF with mathematic derivation and drew the conclusion that,the regular control scheme could be regarded as a composite control with the feedback of DC link voltage and the feedforward of the fundamental load current.The feedforward currents could be regarded as the whole fundamental components of the load current or the active components depending on different compensation objectives.Finally,simulations and experimental results proved the validity of the analysis.