Abstract: The leak rates of He, N₂, N_e, CF₄ and Kr were measured under different inlet pressures with different leaks by the technology of quantitative analysis of quadrupole mass spectrometry in the multi-gas analyzer; and the leak rate equivalent relationship was established by comparing leak rates between different gases under the same working condition. The experimental results show that the relationship between the gas leak rate and the pressure is different when the gas is under different working conditions with different flow types. From the result of He, a leak rate expression is found to be the same with all flow types. The leak rate equivalent relationship of gas is derived with a linear trend under high or low leak rate boundary conditions and with four or five order polynomial trend in between them. However, the leak rate relationship between CF4 and He is linear in all data areas, which shows some differences between polyatomic molecule and monatomic molecule. The results of experiment provide some basic data for establishing the leak rate index of tracer gas.