The atomic structure models of the surface，the interface of oxide scale and bulk of Fe-Cr-Al alloy were set up by using corresponding computer programming, and the electronic structure parameters （environment-sensitive embedding energy，affinity energy，total energy and total density of states） of alloying elements on the surface，the interface of oxide scale and bulk of Fe-Cr-Al alloy, were calculated by the recursion method. The formation mechanism of the oxide film，the influences of sulfur and rare earth metals on the adhesion of oxide film of Fe-Cr-Al alloy and on the formation course of the oxide film were studied systematically on electronic level. The results show that the driving force of Al atom to segregate on to the surface was larger than that of Cr and Y atom. This leads to the inward diffusion of O atoms and the outward diffusion of Al atoms at the early stage of oxidation，resulting in a surface layer rich in Al and O atoms. The affinity force between oxygen and Al was larger （the affinity energy being lower），oxygen is easy to combine with Al atoms to form Al2O3 oxide scale. Yttrium is segregated to the surface，which inhibits the diffusion of Al to the surface of Fe-Cr-Al alloy. The lateral growth of oxide film is effectively controlled，the occurrence of the convoluted morphology of the scale is avoided，the adhesion of the oxide film to the Fe-Cr-Al matrix is increased by the addition of Y. The diffusion of impurity S to the interface of Fe-Cr-Al matrix and Al2O3 oxide scale increases the total energy of the interface，decreases the total density of states，which reduces the stability of the interface，weakens the cohesion of Fe-Cr-Al matrix and Al2O3 oxide scale.