The leak detection for large vacuum system is generally time-consuming and inefficient.In this paper,it was firstly analyzed how the leak test signals come into being.Then the mathematical model of the leak test signal was established,and the final steady leak rate was ascertained.Based on the above analysis,a fast and exact leakage test method was proposed.By this means,the leak detection nethod is not only able to accurately predict the leak rate of the target leak,but also significantly decrease the leak detection time.Thus,it will enhance the leak test efficiency.