Abstract: Surface discharge effect of spacecraft insulating material in space irradiation environment is one of the main factors that threaten spacecraft safety. To investigate the pattern and influencing factors of the electrostatic discharge of polytetrafluoroethylene (PTFE) in complex ionization environment, the flashover voltage of PTFE under high voltage direct current (DC) in high vacuum and during low energy electron irradiation were experimentally obtained, the trap density before and after irradiation was tested by isothermal surface potential decay, and the influencing factors of flashover voltage were analyzed. The results show that the surface flashover voltage of PTFE under the irradiation with electron energy of 19~25keV is higher than that under no irradiation. Higher electron energy leads to smaller positive charge density on surface of PTFE and larger trap density, decreasing deformity of surface electric field, increasing the flashover voltage finally. On the condition that electron energy remains the same, the flashover voltage of PTFE would be lower with the increasing electron beam density, number of initial electrons and number of secondary electrons.