The utility model provides an underground excavated power tunnel, which comprises a tunnel main body and a supporting layer which is arranged on the external side of the tunnel main body. The tunnel main body is provided with a tunnel bore with a square lower part. Cable racks for laying cables are arranged in the tunnel bore. According to the underground excavated power tunnel provided by the utility model, since the lower part of the tunnel bore is designed to be square, the arrangement, the patrol inspection and the maintenance of the cables are facilitated; and since the cable racks are arranged in the tunnel bore, the cables can be effectively fixed.