In a power supply system, when a power supply is inserted into a power interface of the OTG peripheral, the power supply supplies power to a USB secondary device connected to a second USB interface of the OTG peripheral; and when the power supply is inserted into the power interface of the OTG peripheral, the OTG peripheral outputs a high-level pulse by using the first USB interface of the OTG peripheral, so as to trigger a terminal connected to the first USB interface to stop supplying power to the USB secondary device; and in addition, the OTG peripheral enables, after a delay of a preset safe time, the power supply to supply power to the terminal connected to the first USB interface.