Abstract: The homogeneity of electric field in the traditional drift tube is very critical to the performance of ion mobility spectrometry. In this study, numerical simulation of electric field in traditional drift tube was conducted by means of COMSOL Multiphysics software with finite element method. Additionally, modeling method and homogeneity standard for electric field were also presented. The influences of some important factors such as thickness of electrode and insulating ring, inner diameter of drift tube as well as metal enclosure of drift tube, on the homogeneity of electric field were researched. On the basis of the research, some useful laws were concluded. This paper is aimed at optimizing instrument design through the numerical simulation results, which can help designers to improve the performance of ion mobility spectrometry. Compared with the traditional research methods through experimental structure design, the simulation results can help shorten the instrument development cycles and save development costs.