The hydrophobic modification of surface of silicone rubber (SIR) used as insulator was carried out by CF4 radio frequency (RF) capacitively coupled plasma (CCP) and inductively coupled plasma (ICP). The topography and chemical composition of modified SIR samples were characterized by atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. The static contact angle (SCA) was employed to investigate the surface wettability of SIR samples. The results indicate that the molar ratio of Si-F/C-F and the increase of surface roughness of SIR samples treated by CCP processing are higher than those treated by ICP processing. The fluorination and ablation or etching action are parallel and competitive, resulting in the introduction of fluoric groups and the change of surface micro-morphology occurring on the SIR surface simultaneously. The improvement of hydrophobicity is mainly ascribed to the synergistic reaction of the introduction of fluoric groups on the surface of SIR sample and the increase of surface roughness that was created by the ablation or etching reaction of CF4 plasma.