A PoE relay system includes a networking cable, a PoE power injector and a PoE access bridge device. The PoE power injector is coupled to a PoE powering apparatus to receive network data and network power, and to a power supply to receive DC power, and gathers the network data, the network power and the DC power in a gathered signal group. The PoE access bridge device is coupled to the electronic product, receives the gathered signal group, receives the DC power from the gathered signal group for operation, and separates the network data and the network power from each other, and outputs the network power to the electronic product.