Abstract: The slowdown of charge dissipation rate and loss of hydrophobicity after surface contamination are important factors to reduce the insulation performance of silicone rubber (SIR) composite insulators along the surface. In this paper, a normal pressure pulse sliding arc plasma generator was used to modify the surface of artificially polluted high-temperature vulcanized (HTV) silicone rubber at different time (0~3 min). The surface potential measurement system and Fourier transform infrared spectrometer (FTIR) were used to study the effects of plasma treatment on the surface charge motion characteristics, hydrophobicity and chemical composition of contaminated silicone rubber samples, and the surface dielectric properties of contaminated samples before and after treatment were tested. The results show that plasma treatment at different times can accelerate the rate of charge dissipation on the surface of the sample, introduce a large number of shallow traps during the treatment, and decrease the trap energy level depth and trap charge density, which weakens the ability of the sample surface to capture electrons and inhibits charge accumulation. The volume resistivity of the sample is hardly affected by plasma treatment, whereas the decrease of surface resistivity makes it easier for the charge to dissipate along the surface of the sample. After plasma treatment, the surface flashover voltage of the sample is increased under both dry and wet conditions. Plasma treatment restores the hydrophobicity of the samples in a short period of time, and the longer the treatment time, the more obvious the improvement of hydrophobicity; after plasma treatment, more small siloxane molecules migrate to the surface of the dirt layer, making it more hydrophobic.