The invention discloses an automatic leakage rate testing system applied to a large space environment simulator, which mainly comprises a leakage detection module, an auxiliary exhaust module, and an automatic control and data acquisition and analysis module, wherein the leakage detection module is mainly composed of a helium mass spectrometer leakage detector, a leakage detection valve and a leakage hole graded sampling device; the auxiliary exhaust module is mainly composed of an oil-free molecular pump group, a vacuum measuring device and a connecting pipeline; the molecular pump is isolated with a container through a high-vacuum gate valve; the automatic control and data acquisition and analysis module is composed of automatic leakage detection control, data acquisition and man-machine interaction parts; the automatic leakage detection control carries out automatic equipment control according to the optimal logic; the data acquisition is used for acquiring various data through a writable communication protocol; and the man-machine interaction is used for displaying the system operation state and processing data according to test requirements to automatically generate a report.