Ultraviolet (UV) aging is one of the most important problems that electrical insulations are faced with it. Generally, total UV radiation emitted from the sun is divided into three parts. Among all types of ultraviolet radiation, UV _C has the highest energy because its wavelength is less than 290 nm. Therefore, UV _C is definitely harmful for health and even for other objects on the earth including electrical insulators. The objective of the current paper is to study the aging process of silicone rubber insulators exposed to UV _C radiation. To accomplish this purpose, three different kinds of commercial silicone rubber insulators were aged by UV _C radiation and contaminated solution. Then their electrical and thermal properties as well as their changes on the surface were investigated by measuring leakage current, thermo-gravimetrical analysis and surface elements. It is observed that, the effect of contaminated solution on leakage current is more than the influence of UV radiation alone. In addition, combination of UV _C radiation and pollution extremely increase leakage current. Pollution has especially influence on the 3 ^th harmonic component. Aging by UV _C shifts the thermal decomposition temperature of the insulations to lower temperatures and degrades the surface of the systems especially the polymers surround the filler. Also it was realized that UV _C is able to decompose the filler and reduce the Al/Si ratio in the sample.