Abstract: In order to study the variation rule of components in silicone rubber of composite insulators during aging process, various tests are conducted on unused silicone rubber as well as silicone rubber used for 2, 6 and 10 years. These tests includ scanning electron microscopy analysis, thermogravimetric analysis, differential scanning calorimetry analysis, Fourier transform infrared analysis, and X-ray spectroscopy analysis. The relevant results show that during operation, the integrity of silicone rubber molecular chains deteriorates, and more and more cracks and voids appear on the surface of silicone rubber. Additionally, the operation of silicone rubber is closely related to the variation and precipitation of aluminum hydroxide in its components, with aluminum hydroxide experiencing the most significant changes during operation. This study can better reflect the surface aging status of silicone rubber and is of great significance for the formulation design and aging failure analysis of composite insulators.