Abstract: The SiO₂/polytetrafluoroethylene (PTFE) composite films with 35wt% SiO₂ and the thickness of 50 μm were prepared by air-assisted dry blending, cold-pressing, sintering and skiving techniques. The effects of SiO₂ particle size on the pinhole defects and mechanical properties for SiO₂/PTFE composite films were investigated, and the influence of the dispersion of SiO₂ in PTFE and the intermolecular interaction on the mechanism of its performance was also studied. The results show that with the increasing of SiO₂ particle size, the dispersion throughout the PTFE matrix tends to be uniform, and PTFE can coat the particles better. The pinhole defects of the SiO₂/PTFE composite films are reduced and the mechanical properties are improved. When the particle size (D₅₀) of SiO₂ is 12 μm, the distribution in the PTFE matrix is most uniform, the pinhole defects are least, and the PTFE/SiO₂ composite film exhibits optimum mechanical properties. The elongation at break is 19.5%, and the tensile strength is 9.2 MPa.