<p>In this study, to investigate the influence of chromium on the oxidation kinetics of Ni–Fe alloys at high temperatures, isothermal oxidation tests were performed at 800°C through thermogravimetric analysis (TGA). The phase composition and microstructure of the oxidized samples were analyzed through scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The adsorption characteristics of oxygen atoms and the density of states (DOS) of the oxidation products were analyzed by first-principles density functional theory calculations. The results revealed that oxygen atoms preferentially adsorb at the bridge site of the (Cr)FeNi₃ (001) surface and at the hollow site of the FeNi₃ (001) surface. Furthermore, oxygen atom adsorption at the FeNi₃/Cr₃C₂ interface exhibited comparable stability, which may facilitate the formation of a dense oxide film in adjacent areas, thereby inhibiting further oxidation of the material. Additionally, the oxidation kinetics of the Ni–Fe–Cr alloy at 800°C approximately followed a parabolic law. The enhanced oxidation resistance of this alloy can be mainly attributed to the formation of protective oxides such as Cr₂O₃ and NiCr₂O₄ within its oxide layer. This study provides theoretical insights for improving the high-temperature oxidation resistance of Ni–Fe alloys.</p>