Novolac resin was modified by grafting reaction with condensation product of Polymethyl Triethoxy Silane and Polymethyltriethoxysilane, which could be used for curing epoxy resin. The different modified novolac resins were prepared from different ratio of materials and cured with epoxy resins. The cured products were tested by impact strength, glass transition temperature and thermogravimetric analysis. The results showed that the glass transition temperatures of modified cured products was 30℃ higher than the pure product, the impact strength increased more than 36.6%, and the thermal stability better.