Polytetrafluoroethylene (PTFE) and its composites are key materials in the field of seal and new generation information technology. However, due to its unique molecular structure, PTFE resin particles are difficult to form effective compounding with inorganic materials, affecting the function of fillers, so it is necessary to improve the interface synergy between the matrix and functional particles. PTFE composite film materials can be prepared by the emulsion film forming technology independently developed by our team, but the effect of filler and PTFE interface on the comprehensive properties of composite film materials has not been studied. Therefore, in this study, SiO2 with different sizes and contents was mixed with PTFE emulsion to explore the influence of PTFE/SiO2 interface on the properties of composite film materials, in order to prepare composite materials with excellent properties. The results show that the interfacial compatibility of the composites is good, the tensile strength can reach 7.9 MPa, and the elongation at break is 153.3%. Compared with the pure PTFE film, the linear thermal expansion coefficient is decreased by 43%. This study provides the necessary data for optimizing the PTFE mixing interface and preparing PTFE composites with excellent properties.