The invention relates to the field of high-voltage power transmission and transformation equipment experimental technology and in particular to a high-voltage AC isolating switch assembly tool, whichcomprises a base, wherein an input shaft positioning hole for inputting an input shaft and an input shaft positioning member for fixing the input shaft are arranged on the base; the base is further provided with a transmission shaft positioning hole for a transmission shaft to penetrate through downward. The high-voltage AC isolating switch assembly tool further comprises a drill jig positioning plate and a drill jig positioning member for fixing the drill jig positioning plate. The drill jig positioning plate is equipped with a processing hole and a positioning hole. The same plane where thecenter line in the front-rear direction of the positioning hole and the axis of a drill jig are located forms a positioning plane. The drill jig positioning plate has a positioning plane coplanar withthe axis of the drill jig. The positioning plane has the same distance to the front and rear walls of the positioning hole, wherein the distance is equal to the radius of the portion of the output shaft matching the positioning hole. An assembly process can be realized by installing parts on the corresponding positions. The tool is simple in structure and high in assembly efficiency.