Abstract: SiO₂ / cyanate ester (CE) nano-composites were prepared by a high-speed homogeneous shearing method ;the quasi-static and dynamic mechanical properties and the thermal stability of the composites were investigated. Theresult s show that the impact and flexural st rengths of the composites obviously increase at the low content of SiO₂ .The impact st rength reaches a maximum at 0. 30 wt % SiO₂ , which is 88. 9 % higher than that of the pure CE. Andthe flexural st rength reaches a maximum at 0. 15 wt % SiO₂ , which is 20 % higher than that of the pure CE. Thestorage modulus and high temperature loss modulus of the composites obviously increase compared with those of thepure CE , and the glass t ransition temperature is 31. 2 ℃ higher than that of the pure CE. It is also found that thedecomposition temperature of the composites reaches a maximum at 0. 30 wt % SiO₂ ; when the mass loss of composites is 10 % , the degradation temperature increased by 25. 7 ℃compared with that of the pure CE.