Abstract: Effect of Ag film and TiO2 film thicknesses on the optical properties of TiO2/Ag/Ti/TiO2 film system were simulated by using TFCalc software, and TiO2/Ag/Ti/TiO 2 low-emissivity films with different Ag film thicknesses were prepared by electron beam (E-beam) evaporation method according to simulated results. The results show that the critical thickness of Ag film to form a continuous film was about 15 nm, and the visible light transmittance of low-emissivity glass with the critical thickness was 81% and W70 was closed to 330 nm, while the high visible light transmittance could not obtained when the films thickness was 20 nm.