Abstract: Due to its excellent pollution resistance, composite insulators are widely used in China's power grid. However, with the growth of the service life of composite insulators, a huge number of silicon rubber materials which are difficult to degrade naturally from decommissioned composite insulators will bring great pressure on the environment. In this paper, based on the method of pyrolysis, a green method of recycling waste composite insulators to obtain high economic value products is proposed. Firstly, the composite insulator silicon rubber materials, which were naturally decommissioned after 20 years of operation were collected. The pyrolysis process of the silicone rubber material and the products of the solid and gas were studied in detail, which preliminarily verified the feasibility of the method. Then the physicochemical properties of products at different heating temperatures and socking time were compared, and the optimal parameters of the pyrolysis process were obtained based on the growth model of ultrafine particles. Finally, the purity and particle size of the nanoparticles were analyzed and compared with commercial silica. The research results show that the waste silicone rubber materials can be greenly decomposed by pyrolysis. Under the condition of 700 ℃ for 120min, the central particle size of nano-silica is 160 nm, the purity is more than 97%, the particle size is uniform, the shape is smooth, and the performance is better than commercial silica.