The silica grafted graphene oxide (SiO2-gGO) was synthesized using graphene oxide, silicon sol and toluene diisocynate as raw materials, and its reinforced epoxy composites were fabricated through ultrasonication and the cast molding method. The SiO2-g-GO/epoxy composites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, dynamic mechanical analysis and scanning electron microscopy. The results show that the impact strength of composites increases to 38.79 kJ/m2 and is about 2.2 times of that of the pure epoxy resin when the content of SiO2-g-GO is 5phr. Meanwhile, tensile strength, bending strength and elastic modulus increase by 1.35 times, 1.45 times, 1.42 times, respectively. The thermogravimetric and dynamic mechanical analysis indicates that the decomposition temperature, maximum decomposition rate, the storage modulus and glass transition temperature of the composites are improved. The SEM micrography of impact fracture shows that SiO2-g-GO of epoxy has the significant toughening effect.