The duplicate rectifier’s control strategy and principle are researched. Besides this paper derivers a formula for calculating support capacitor from the relation of power transfer in rectifier. Established simulation model of Traction Power Supply System based on Matlab/Simulink, in order to build platform of Traction Power Supply System’s load condition on digital simulation tests. Through coupling the simulation model of Traction Power Supply System and PWM rectifier, analyzes adaptability of PWM rectifier when the fluctuation of the supply conductor voltage. So we need cut down the railway vehicle’s power when the voltage too low or too high.