Abstract: To improve the dispersibility of nano SiO₂ particles in silicon rubber (SR) and the interfacial bonding performance of the two phases, the surface modification agent consisting of hydroxyl silicone oil (HSO) and 3-(trimethoxysilyl)propylmethacrylate (KH570) for nano SiO₂was designed. And the modified nano SiO₂/SR composites were prepared. The morphology structure of nano SiO₂ and the dispersibility of nano SiO₂in the ethanol were investigated, the fracture surface morphology, mechanical properties and thermal stability of the modified nano SiO₂/SR composites were also analyzed. The results show that KH570 is successfully grafted to the surface of nano SiO₂ and formes chemical bonds with the SR matrix. When the nano SiO₂ is treated by the hybrid surface modification agent (HSO cooperated with KH570), the dispersibility of SiO₂ in SR matrix, and the interface bonding performances between SiO₂ and SR are improved obviously, the mechanical properties and thermal stability of the SiO₂/SR composites are also enhanced significantly. When SiO₂:HSO:KH570 mass ratio is 2.0:0.2:0.6, the initial temperature of thermal decomposition of the modified nano SiO₂/SR composite increases to 230℃. When SiO₂:HSO:KH570 mass ratio is 2.0:0.2:0.45, the tensile strength and elongation at break of the modified nano SiO₂/SR composite increase twice, respectively.