The invention discloses a power supply system for a substation. The power supply system comprises: a power receiver used for receiving a high voltage output by a power plant; a transformer used for transforming the high voltage into an alternating current required for a load; a power supply apparatus used for outputting the alternating current to the load; a controller used for sending a standby power supply enable instruction to a standby power supply when the power supply apparatus has a fault and sending a standby power supply disable instruction to the standby power supply when the fault of the power supply apparatus is eliminated; the standby power supply used for supplying power to the load when receiving the standby power supply enable instruction and stopping power supply to the load when receiving the standby power supply disable instruction; and a charging apparatus used for charging the standby power supply when the chargeability of the standby power supply is lower than first chargeability and stopping the charging of the standby power supply when the chargeability of the standby power supply reaches second chargeability, wherein the second chargeability is greater than the first chargeability. According to the power supply system, the technical problem of relatively poor stability of the power supply system for the substation is solved.