The surface charge accumulation of insulating materials is one of the important factors affecting the vacuum surface flashover at low repetitive pulse voltage. In this paper, electrostatic probe method is used to test the influence of pulse voltage repetition times on the surface charge accumulation characteristics of alumina ceramics. The results show that the surface charge accumulation t of alumina ceramics have a hreshold effect, and there is no charge accumulation on the surface of alumina ceramics at low voltage, which has nothing to do with the times of voltage loading. When the loading voltage reaches a level, a large number of positive surface charges are appearances. With the increase of voltage, the surface charge accumulation increases. When the surface charge density is up to about 8000 pC/cm2, the surface flashover occurs and the surface charge decays rapidly to the order of 100 pC/cm2. The effect of surface charge on the electric field distribution of insulating samples is simulated. The results show that the distortion of electric field caused by surface charge is positively correlated with the voltage amplitude.