SiO2 is one of important low refractive index materials, and SiO2 films are prepared by both ion-beam sputtering (IBS) and electron-beam evaporating (EB) technology. Dielectric constants of SiO2 films are calculated by infrared spectrum inversion technique in a wavenumber range from 400 cm-1 to 1500 cm-1. Through analyzing dielectric energy loss function, the oscillation frequency and the Si–O–Si angle of two types of SiO2 films are obtained in the transverse optics and longitudinal optics oscillating mode. The research results indicate that the attended modes of SiO4 are main coesite-like structure, three-plane folding ring structure, and keatite-like structure in the range of short-range order for EB-SiO2 films, but the attended modes of SiO4 are main coesite-like structure, three-plane folding ring structure, four-plane folding ring structure, and keatite-like structure in the range of short-range order for IBS-SiO2 films.