Leak rate is one of the key factors that affect the storage life and working life of detector/dewar assembly, and also the major parameter for estimating the vacuum perfection of military dewar. Especially, the mini-leak which is difficult to be probed by conventional leak detection method is the major factor that affect the producivity of military dewar. In this paper, the methods, basic principle and test results of several kinds of super sensitive leak detection are described. And according to the requirement of military dewar, the corresponding leak detection method for the research and production is selected.