One of the most significant synthetic functional elastomers is silicone rubber (SR), which has special properties like thermal and chemical resistance, high weathering and oxidation resistance, low-temperature toughness, electrical insulation, and high optical transparency. Elaboration thermal and mechanical capabilities however are needed for the SR's ever-expanding applications. The effect of modified CeO2 powder loaded in silicon rubber composites on the thermal and mechanical properties was investigated. The impacts of surface modification of CeO2 powder content on silicon rubber composite characteristics were discussed. Silicon rubber nanocomposites were prepared by inclusion different concentrations of 2, 5 and 10 phr of the surface modified cerium oxide. The effect of radiation on the mechanical properties (TS, E %) at different doses was investigated. The thermogravimetric analysis (TGA) of the nanocomposites was studied. The volume resistivity was also measured. The results indicated that the nanocomposite contains 5 phr of CeO2 and irradiated to 100 kGy has the best properties and it has a wide range of industrial uses as effective thermal and electrical insulating materials.