The invention discloses an ultrasonic positioning device and method for a GIS withstand voltage breakdown fault. The method comprises the steps that ultrasonic signals are collected through multiple ultrasonic sensors arranged on a shell of a cavity of a GIS interval air chamber, subjected to filtering, amplifying and A/D conversion by a signal processing module and output to a data analysis module; when the processed signals meet preset conditions, it is judged that the positions where the ultrasonic sensors collecting the ultrasonic signals are located are suspected fault locations; firstly, the position of a detection point with the maximum signal amplitude is determined, and then the detection point is judged to be a suspected fault location or not by judging whether the range of the difference between signal duration at the detection point and signal duration at an adjacent detection point is within a preset range, namely, the suspected fault location can be determined just through one-time obtaining of the ultrasonic signals. Consequently, the problem that when a scheme in the prior art is adopted, insulation damage is caused to a normal GIS part is avoided.