A power extension wire includes a power plug, a socket, and a cord connected between the power plug and the socket. The power plug includes a wireless transmission module, the socket includes an alternating-current jack and a current converting unit. The cord includes a plurality of alternating-current conducting wires and at least one direct-current conducting wire. The current converting unit receives an alternating-current power through the alternating-current conducting wires and provides a direct-current power to the wireless transmission module through the direct-current conducting wire.