The invention relates to special equipment for drilling and reaming a large scale equipment dowel hole. The special equipment is composed of a portal frame, a main shaft box, a drilling device, lead screws, rotating wheels, guide rails and a control device. Supports on two sides are connected with a top beam, a transverse beam is arranged in the middle, a rotating wheel is arranged on the lower side of each support, two guide rails are arranged on the lower sides of the rotating wheels, and therefore the portal frame capable of moving forwards and backwards and braking is formed. The lead screws are arranged in the two supports and the transverse beam, the supports and the transverse beam are connected through guide rail armature iron pressing plates, the transverse beam can move vertically on the portal frame formed by the supports, the main shaft box is installed on the transverse beam, the drilling device is installed in the main shaft box, the main shaft box and the drilling device can move horizontally on a guide rail of the transverse beam, and tightening blocks are installed in the main shaft box and the drilling device. Processing of the dowel hole of large scale equipment is convenient, locating is accurate, stable, high in power and high in efficiency in the process of machining, holes which cannot be machined via a drilling machine can be machined by the special equipment, and machining range of hole drilling and reaming is enlarged.