<p>This study developed a multi-scale model that integrates cellular automaton and finite element method. The model is used to investigate the oxidation behavior of AlCoCrFeNi high-entropy alloy under coupled high-temperature and tensile stress conditions. The effects of temperature, grain size, and applied stress on oxidation kinetics were investigated. The simulations reveal that oxidation kinetics follows a parabolic law within the temperature range of 1073–1273 K. Elevated temperatures significantly accelerate elemental diffusion and interfacial reactions, leading to a sharp increase in oxidation rates. Grain boundaries act as critical short-circuit diffusion paths, with grain refinement offering additional rapid transport channels for oxygen ions, further accelerating the overall oxidation process. According to the model prediction, elevating the tensile stress from 100 to 400 MPa can amplify the local oxidation rate by a factor of 1.5 to 35 compared to the stress‑free condition, under the current phenomenological assumptions. This enhancement stems from stress concentration, which triggers localized plastic deformation, elevates the chemical activity of metal atoms, and thereby transforms pit roots into active reaction sites. As oxidation progresses inward under increasing stress, initially isolated plastic zones expand and interconnect, inducing more extensive plasticity. This stress-induced mechanochemical coupling is predicted to compromise the formation of a protective oxide scale. It also promotes short-circuit diffusion networks, which may alter the overall oxidation mechanism.</p>