A low-voltage char pile system for a direct current power network relate to that field of charging piles. Comprises a DC line network power supply system, a DC input charging pile and a depressurizingdevice, wherein the depressurizing device comprises a main control unit, an analog-to-digital conversion module, an IGBT module Q, a filter circuit, a current-voltage sensor and a DC relay S sequentially connected between the DC line network power supply system and the DC input charging pile; The current-voltage sensor is connected with an analog-to-digital conversion module, the analog-to-digital conversion module is connected with a main control unit, and the IGBT module Q is connected with an output terminal of the main control unit through an IGBT driving circuit. The control end of the DC relay S is connected with the main control unit. By sampling the input voltage and current, comparing with the input threshold and controlling the duty ratio of the IGBT driving circuit, the invention can reduce the input voltage in an effective time range and protect the DC input charging pile.