Abstract: Ion trap mass spectrometry has been widely used in mass analysis. In the process of mass analysis, there are several operation modes for the ion trap, and different operation modes result in different ion emission modes. In the process of mass spectrometry analysis, the chamber has a high requirement for the vacuum. Based on the ion motion theory, by selecting an appropriate collision model, different ion emission modes are simulated from 10^-3 Pa to 100 Pa. The influence of various conditions on the mass resolution under different emission modes is researched. The simulation shows that when using scanned radio frequency (RF) voltage and voltage application with constant auxiliary alternating current (AC) voltage, the mass resolution is affected by the ion collision probability and the kinetic energy applied by the alternating electric field. At the same time, applying appropriate auxiliary alternating sweeping voltage can avoid the ion excitation in advance or relaxation lag excitation and further improve the resolution. At present, there is no quantitative analysis of this theory. Finally, through the optimization of the emission mode, the simulation realized that the mass resolution of 220 is achieved under the pressure of 100Pa. Compared with the boundary unstable emission mode, the mass resolution was increased by 185%.