A network device of a power over Ethernet system, the network device comprising a power system, a processor, a power sourcing equipment PSE chip, a first forward power supply port, a first powered device PD chip, and a first reverse power receiving port, wherein the PSE chip is connected to the first forward power supply port; the first PD chip is connected to the first reverse power receiving port; the processor is connected to the PSE chip; a first powered device is connected to the first forward power supply port and the first reverse power receiving port; the power system is configured to supply power to the processor and the PSE chip; the PSE chip is configured to: when the network device is supplied with power by a power source, supply power to the first powered device by using the power system through the first forward power supply port; the processor is configured to: when detecting that a power failure occurs on the network device, instruct the first PD chip to draw power from the first powered device; and the first PD chip is configured to: when the power failure occurs on the network device, draw the power from the first powered device through the first reverse power receiving port, and supply the obtained power to the power system, wherein the first powered device receives power input from a local power source; the processor is further configured to: calculate a second supply power based on a first supply power, wherein the first supply power is a power of electric energy drawn through the first reverse power receiving port, and the second supply power is a maximum power used when the PSE chip supplies power to at least two devices other than the first powered device by using the power system; and determine one or more target powered devices based on power supply priorities of the at least two devices, and the required powers corresponding to the at least two devices, and the second supply power; and instruct, the PSE chip to supply power to the one or more target powered devices by using the power system; the PSE chip is further configured to: supply power to the one or more target powered devices, according to the instruction of the processor to supply power to the one or more target powered devices. when detecting that a power failure occurs on the network device, instruct the first PD chip to draw power from the first powered device; and the first PD chip is configured to: when the power failure occurs on the network device, draw the power from the first powered device through the first reverse power receiving port, and supply the obtained power to the power system, wherein the first powered device receives power input from a local power source; the processor is further configured to: calculate a second supply power based on a first supply power, wherein the first supply power is a power of electric energy drawn through the first reverse power receiving port, and the second supply power is a maximum power used when the PSE chip supplies power to at least two devices other than the first powered device by using the power system; and determine one or more target powered devices based on power supply priorities of the at least two devices, and the required powers corresponding to the at least two devices, and the second supply power; and instruct, the PSE chip to supply power to the one or more target powered devices by using the power system; calculate a second supply power based on a first supply power, wherein the first supply power is a power of electric energy drawn through the first reverse power receiving port, and the second supply power is a maximum power used when the PSE chip supplies power to at least two devices other than the first powered device by using the power system; and determine one or more target powered devices based on power supply priorities of the at least two devices, and the required powers corresponding to the at least two devices, and the second supply power; and instruct, the PSE chip to supply power to the one or more target powered devices by using the power system; the PSE chip is further configured to: supply power to the one or more target powered devices, according to the instruction of the processor to supply power to the one or more target powered devices.