Abstract: Ionization vacuum gauges are widely used in ultra-high vacuum measurement and are currently the only practical ultra-high vacuum measurement instruments. For different gas environments, the ionization cross section of the vacuum gauge is different and has a significant impact on the measurement sensitivity. Based on the BEB electron impact cross section model and numerical simulation algorithm, the ionization cross section of different gases in the ionization region of the vacuum gauge was calculated, and the variety of relative sensitivity of vacuum gauge was measured. The results show that in the pressure range of 10^-8-10^-5 Pa, the relative sensitivity distribution deviation of Kr, Ar, CH₄, CO₂, He gas in the vacuum gauge is only 4.78%, and the measured relative sensitivities of different gases are 2.01,1.46, 1.66, 1.45, 0.198. The simulation results are in good agreement with the experimental results.