In order to look into the internal structure and electrical properties of insulating Silicone rubbers added reinforcing fillers; Silica(0∼140 phr), and to examine the behavior of charged particles, and the properties of thermally stimulated current (TSC) are investigated, respectively. From the TSC which are formed by applying the electric field of 2∼5 kV/㎜ to specimen at temperature range from -150 to 270℃, the results are as following. In the case of non-filled specimen, four peaks of δ, γ, β and α are obtained at the temperature of -120℃, -60℃, 20℃ and 130℃, respectively and the case of filled specimen, three peaks of δ, α₂ and α₁ are observed at the temperature of of -120℃, 80℃ and 130℃, respectively. The origins of these peaks are that, the δ peak seems to the result from the contribution of side chain methyl radical, and the β peak from the depolarization of space charge polarization owing to added imputity during during manufacturing specimens, and the β peak from the orientation of Si-CH₃ dipole, and the α₂ near the temperature of 130℃ from carboxyl acid that is formed by the thermal oxidation of high temperature.