Under the conditions of vacuum and different temperatures, surface charging of polyimide materials is carried out by electron gun irradiation, and their surface potential decay characteristics with time are measured. Variation of conductivity with temperature is obtained, and the trap distribution of polyimide at different temperatures is calculated combining with theory of isothermal surface potential decay. With the increasing of temperature, the number of shallow traps in polyimide increases gradually, and that of deep traps reduces gradually. The variation rule of shallow traps is proportional to the conductivity of polyimide, that is to say, the more the shallow traps are, the stronger the migration of carriers will be. Research results can provide a useful reference for the modification of anti-aging and anti-flashover of polyimide materials.