High voltage insulators are essential for the reliable performance of electric power systems. Polymeric insulators are widely used as outdoor H.V insulators. In the presence of heavy polluted and wet condition, resistance to vandalism and high dielectric strength voltage. Polymer insulators particularly those made of Ethylene Propylene Diene Monomer and silicone rubber are increasingly being used today. Blending of two polymers is an attractive way to develop a new material combining the best properties of these two materials. In 1986 the first alloy of silicone rubber/EPDM was prepared. Today the most widely used insulators weather shed materials are silicone rubber /EPDM blends. This paper aims to improve silicone rubber /EPDM blends electrical properties by adding SiR to EPDM in different percentages. Also aims to study dielectric strength and tracking resistance under several conditions of SiR/ EPDM blend samples. Then trying to find an appropriate weight percentage composition of such blend in order to enhance the dielectric strength and tracking resistance in different conditions.