SiO2 nanophotonic film is widely used in the areas of photovoltaic, nanophotonics and microelectronics. Plasmaassisted electron beam evaporation was used to produce the SiO2/Si nanofilm at low temperature. By using the ellipsometric method，we studied the optical properties of the nanofilms under three different process conditions, such as deposition rate, substrate temperature and radiofrequency power. The best condition to make the SiO2/Si nanofilm was obtained. The studies of the mechanical, chemical and optical properties of the SiO2/Si nanoflim show that the nanofilm prepared with plasma assisted electron beam evaporation under the best condition is superior to that produced by the conventional methods.