Abstract: SiO2 films were deposited on fused silica substrates by ion beam sputtering(IBS) technology, and the effects of thermal treatment on structural characteristic were researched. The effects of annealing temperature on surface roughness of IBS-SiO2 films were very large, low annealing temperature could reduce the surface roughness, but high annealing temperature could increase the surface roughness, the proper annealing temperature had almost no impact on surface roughness. Amorphous structures of IBS-SiO2 films were researched by XRD technology. When the annealing temperature was 550 ℃, the largest short range order and the shortest average distance were obtained, the results were the same as the fused silica substrate, and the structure was stable. Expermental results show that structural characteristic of IBS-SiO2 films can be improved by the proper thermal treatment.