The switch is applicable to three -phase oil-immersed transformer with AC 10kV, 50Hz or 60Hz, equipment highest voltage of 12kV and below and rated current of 400A and below. This switch uses vacuum tube to replace the traditional copper tungsten alloy to change the load current, so it solves the problems of frequent switch, burn out of arc contact, carbonization of insulating oil, then improves the mechanical and electrical life. The maintenance cycle is prolonged and the maintenance cost is reduced.