Abstract: Silica nanoparticle synthesized by aerosol method was the best reinforcing filler for HTV silicone rubber. The influence of the structure of silica nanoparticles and their dispersion among the silicone rubber were investigated. The results show that the silica aggregates between the size of 100~200 nm have a better reinforcing function to the silicon rubber. The optimum reinforcement in silicon rubber is ~obtained when added with 35~40 g untreated silica nanoparticle per 100 g rubber. Microcrystlline ~region is formed by silica nucleus when added with silica nanoparticles in silicon rubber, which ~enhances the physical cross-linking and crystallization easily.