Abstract: This paper studies the influence of various aspects of the pressure and composition of the mass calibration standard gas, which is of great significance to improve the preparation accuracy of the standard gas at the launch site, and to realize the accurate calibration, performance evaluation, and in-orbit fault analysis of the new generation of rocket bulkhead leakage monitoring system.Through the research of molecular flow injection technology, accurate measurement technology of calibration chamber volume, and the best working parameters of mass spectrometer, the purpose of accurate control of standard gas pressure and components is achieved.A portable standard gas generator was designed by analyzing the factors affecting the pressure and composition of the standard gas for mass spectrometry calibration.The time stability test of the calibration coefficients of oxygen-nitrogen and hydrogen-nitrogen was carried out using the standard mixed sample gas.The results showed that the calibration coefficients measured by the multi-ion scanning mode of the mass spectrometer were larger than those measured by the simulated peak detection mode. However, with the extension of time, the calibration coefficients measured by the two modes had good stability, and the equilibrium time was about 2 hours.