A fixing device for a GIS partial discharge ultrasonic positioning sensor is characterized by comprising a metal fixing seat (1), an elastic rubber pad (2), a hard rubber sleeve (5), a hook (8), a length adjustment buckle (9) and an elastic band (10), wherein the metal fixing seat is formed by fixing a short circular pipe in the center of a block-shaped metal base plate, symmetrical fixing holes (4) are opened, at the two sides of the short circular pipe, in the base plate, the cylindrical hard rubber sleeve is superposed and embedded into the short circular pipe, the elastic rubber pad is arranged at the bottom of the hard rubber sleeve, a gap used for sensor wiring is opened in a side edge of an opening part of the hard rubber sleeve, one end of the elastic band is fixed in one fixing hole through the hook, and the other end of the elastic band is buckled in the other fixing hole through the length adjustment buckle. With the fixing device adopted, an ultrasonic positioning sensor can be conveniently fixed on a GIS housing to achieve the effects of sliding prevention and shock absorption, and the sensor and the housing can be in close contact through the elastic band and the elastic rubber pad.