The silicone rubber of the composite insulator is critical to the silicone rubber's operation time. To study the changing pattern of silicone rubber composition and silicone rubber operation process, 2, 6 and 10 years of composite insulator silicone rubber were chosen for testing, which included scanning electron microscopy analysis, thermogravimetric analysis, differential scanning calorimetric analysis, fourier infrared analysis, and X-ray spectroscopy analysis. The correlation results show that the integrity of the silicone rubber molecular chains deteriorates during operation, and an increasing number of cracks and holes appear on the silicone rubber surface. The operation of silicone rubber is related to the change and precipitation of aluminum hydroxide in silicone rubber components, and aluminum hydroxide changes the most during operation. This research can better reflect the surface aging state of silicone rubber sheds, which can be used for formulation preparation, quality inspection, operation condition assessment, and aging failure analysis of composite insulators.