Abstract: Circularly compared measure of search gas sample data,end data and beginning data is used.The standard search quantity gas is directly injected into cumulating room to calibrate the leak rate of multi-system spacecraft.The problems of the linearity and repeat in long time for quadrupole mass spectrometer (QMS) measure are avoided.The apparatus of leak detection of multi-system spacecraft with GAM500 mass spectrometer was manufactured.In the air environment the sensitivity of minimum leak detection is 10 -6Pa·m 3/s.The leak detection results of new multi-system spacecraft are introduced.The reliability is increased.The leak detection time and the leak detection cost are cut down.