Abstract: Polytetrafluoroethylene(PTFE) is often used in spacecraft cable production for its excellent insulation and chemical stability. To study the surface flashover characteristics of PTFE, we conducted experiments under normal atmospheric pressure, with the DC voltage applied at the two ends of the PTFE samples, and the discharge voltage value, voltage and current waveform were obtained. The results show that with the increase of the number of flashovers, the discharge voltage increases at first and then stabilizes, and the average field strength is reduced. It is concluded that the change of the surface roughness and the chemical properties of the surface are important factors that influence the surface flashover voltage. According to the influence of the number of flashovers on the voltage, a method to describe the PTFE flashover voltage is proposed.