Thermal and weather stability, water repellency, high surface resistivity and lightness have made silicone rubber very attractive materials for polymer insulator. Those features come from the nature of silicone polymer (polydimethylsiloxane). Silicone rubber has been used for high voltage insulation from 1960's and since then physical/electrical properties and durability have been modified. And processability and design of silicone insulator have also been investigated. Another advantage of silicone is the recovery of hydrophobicity on the surface and it can be used even in heavy environment. There are three different curing systems for silicone rubber i.e. peroxide cure, addition cure and condensation cure. A brief explanation for those is made.High loading of aluminum trihydrate (ATH) is commonly used for silicone rubber to improve tracking and arc resistance. Silicone rubber with 50wt% ATH will pass 4.5kV tracking resistance and it also has good resistance to sea wind. Silicone rubber without ATH can be used where sea wind doesn't have much effect. Tracking resistance can also be strengthened by improving hydrophobicity of the surface. Low permanent set silicone rubber is used for indoor/outdoor cable accessories. Another application for silicone rubber for this area is the coating material to give water repellency on the insulator.