Abstract: The electronic structure of Ag₂O nanofilms was theoretically calculated in the first principle method based on density functional theory.The influence of the low index planes and thickness on the optical properties and stability was investigated.The results show that the crystal planes and film thickness have a major impact.To be specific, the refractive index and dielectric function of Ag₂O nanofilm were lower than those of bulk Ag₂O in the visible light range; however, as the thickness increases, the refractive index and dielectric function of Ag₂O (100) and (110) planes approach to those of the bulk.Bulk Ag₂O has a larger extinction coefficient than Ag₂O (100), (110) and (111) planes; and Ag₂O (111) has a much smaller absorptance than the other two planes, especially in the 21^st and 24^th layers.We suggest that the optical and magneto-optical storage devices made of Ag₂O nanofilms have higher transmittance.