The adsorption and diffusion of N on c-Fe–Al (111) surface have been investigated using the first principle calculations combined with density functional theory to explore the formation mechanism of AlN in the oxidation process of austenitic stainless steel. The results indicate that the most preferential adsorption site of N on the surface of c-Fe (111) is fcc-hollow site. In addition, the stable positions are located at fcc adsorption site on clean and Al-doped c-Fe (111) surface adsorbed 4.76 at.% N. Compared with the pure Fe system, c-Fe–Al (111) system reduces the energy difference of N from the surface to the bulk. The system is most stable for 9.09 at.% N adsorbed on the octahedral interstice of the 2nd and 3rd atom interlamination of c-Fe–Al (111) surface. Thus, the doping of Al makes it easier to spread N on the surface of c-Fe (111). The increase in N in the atmosphere also accelerates the diffusion. Moreover, according to the density of states analysis, the interaction between Al and N was enhanced when 9.09 at.% N was adsorbed on the surface of c-Fe–Al (111).