A power transformation device of a powered device in a power over Ethernet system includes a first transformer coupled between a first pin and a second pin of an Ethernet terminal, a second transformer coupled between a third pin and a sixth pin of the Ethernet terminal, and a bridge rectifier coupled between a center tap of the first transformer and a center tap of the second transformer, for rectifying power outputted from the center taps of the first transformer and the second transformer, so as to provide power for the powered device.