Active power filter is usually equipped with large inductors and electrolytic capacitors, which occupied a large part of the equipment volume, cost and weight. The accurate values of these two components also have a great impact on the APF compensation effect. Facing the requirements of large capacity harmonic compensation, the volume and cost of APF system need to be further reduced. This paper carried out a detailed study of the APF main circuit parameter design, and proposed a reasonable calculation method for grid connected coupling inductance and DC capacitance. Simulation and experimental results verify the validity of this method.