Abstract: In view of more and more debris in space, it is an important issue to locate the leak point in manned spacecraft cabin. In this paper, a leak detection method is developed for spacecraft on orbit using circular ultrasonic array sensors. The time difference of the ultrasonic signal reaching different ultrasonic units is calculated by cross correlation, and then the direction of the leak is determined. The leak location can then be identified by triangulation with three ultrasonic array sensors.