Abstract: Polytetrafluoroethylene(PTFE)-based composites filled with nano-sized SiO2 were prepared by sol-gel process,mechanical mixture process and sintering.The hardness of composites was studied and the microstructure analysis was conducted with scanning electron microscopy and X-ray diffraction.The results showed that sol-gel process could make the nano-SiO2 dispersed in the PTFE homogeneously,the hardness of PTFE was increased and the crystallinity of PTFE was reduced.