The invention relates to a power system power-over-Ethernet device and method. A data access port is connected with a signal input device through a network cable; an over-current protection module is connected with an input power source through a network cable; a data and power synthesis port is connected with a power receiving end device through a network cable; and vacant pins of the data and power synthesis port supply power for the power receiving end device. With the power system power-over-Ethernet device and method adopted, the process of power-over-Ethernet in a power system can be simplified; equipment cost and power consumption of the power-over-Ethernet of the power system can be effectively reduced; an illegal external connection-prevention function can be realized, and therefore, the security and stability of the power system can be ensured. The over-current protection module is adopted, when output current exceeds a threshold value, the over-current protection module acts, so that power supply for the power receiving end device can be cut off, and therefore, short circuit faults and damage to wires and equipment can be prevented.