The invention provides a train power supply system in one embodiment. The train power supply system comprises at least a single-phase uncontrollable rectifier circuit, a multiple step-down chopper circuit and a drive control unit, wherein the single-phase uncontrollable rectifier circuit is used for rectifying the input AC power and converting the AC power into DC power; the multiple step-down chopper circuit is used for performing pulse modulation on the DC power according to the control instruction of the drive control unit, adjusting the output voltage of the DC power and outputting a power supply voltage. The train power supply system is capable of reducing voltage ripple, improving the voltage stability and improving the control accuracy of the output voltage.