We studied the changes of both the surface morphology and the surface oxidation state of metal Sn thin films due to oxidation at enhanced temperatures(300—550℃). With atomic force microscopy, it was observed that the metal Sn thin film and the oxidized metal Sn thin films consisted of a great number of square-metallic crystallites and spherical-oxidized agglomerates, respectively. Such changes in the surface morphologies resulting from the oxidation process suggested that the oxidation of the square-metallic crystallites at the enhanced temperatures was anisotropic. By using X-ray photoelectron spectroscope, it was found that there were some oxygen particles adsorbed on both the surfaces of the metal Sn thin films and the oxidized metal Sn thin films. Furthermore, the forms of the adsorbed oxygen particles depended on the surface oxidation states.