This paper analyzes the parameters of power-supply network and the harmonic characteristics of loads by researching the structures and operation ways of traction power-supply system of the train. It also analyzes and compares the current methods in removing current harmonics. Eventually, it comes up with the way using chain high-voltage APF to eliminate the harmonics. This paper describes the main circuit design and control strategy, among which the key technologies are chain APF harmonic detection algorithm, phase-splitting instantaneous current control and balanced DC voltage control. It builds up a simulation model based on actual parameters, and the simulation results show the compensation waveforms and effects which proves the project is feasible and effective.