SiO2 coatings were deposited on silver foils substrate by sol–gel method and their atomic oxygen (AO) erosion resistance was tested in a ground-based AO simulator. The surface morphologies and structures of the SiO2 coatings were investigated by Scanning Electron Microscopy (SEM) 、X-Ray Photoelectron Spectroscopy (XPS). The experimental results clearly demonstrate that this kind of coatings provided a good protection from AO attack. The erosion yield of the coatings was 2×10-26 cm3/atom, decreased by 30 times compared with that of the uncoated silver foils. This SiO2 layer significantly retarded the penetration of oxygen atoms, preventing further oxidation of the bulk silver. It was found that after AO exposure, the film structure tends to transfer from SiOH to amorphous SiO2. This implies that a more stable amorphous SiO2 structure could be formed in sol-gel SiO2 film during AO exposure. The results demonstrate that the coatings prepared by sol-gel technique can protect the silver from atomic oxygen erosion and can be used easily for practical application.