For the AC power-regulating circuit with impact load, this paper analyzes the periodic characteristics and the abrupt characteristics of the current. In order to solve the problem of accurately and quickly tracking and controlling the rapid change of output current of the active power filter (APF) when the load changes suddenly, the traditional PI control algorithm of APF is improved. Based on the idea of repetitive control and the characteristics of harmonic distribution of AC power circuit, this paper proposes a novel PI-PR-repeat feed-forward control algorithm of APF. In which PR control suppresses the fractional harmonic which is lower than the 50Hz. The compensation effect of AC power-regulating circuit under different working conditions is simulated. The results prove that the proposed novel algorithm can effectively reduce the direct current deflection with smaller THD and better compensation effect. When the physical device is put into operation, the actual operation results are consistent with the simulation results.