Abstract: The pollution flashover of silicone rubber (SR) insulators caused by loss of hydrophobicity is a potential risk for stable operation of power system. To operate online and quickly improve the hydrophobicity of contaminated SR surface, pulsed high-voltage power supply was used to generate gliding arc (GA) plasma with ambient air as the carrier gas. Modification was carried out on different species natural polluted SR samples and SR samples after artificial contamination with different non-soluble deposit density. The results showed that the hydrophobicity of the bird droppings fouled SR samples was obviously increased in short time. For the artificial pollution SR samples with a non-soluble deposit density of 0.125 and 0.25 mg/cm², the contact angle increased from about 48° to more than 130° after 60~90 s of scanning. The same effect could not be seen in samples without GA plasma treatment after several days of natural migration. Optical emission spectroscopy (OES), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy analysis revealed that the GA plasma breaks the compact structure of the contamination layer and produces large number of micropore, which makes it faster for the low molecular weight siloxanes (LMWs) in the SR to migrate to the contamination layer surface. The results of the pollution flashover test show that the pollution flashover voltage of the artificial polluted samples after GA plasma treatment has been greatly improved.