Abstract: It was discovered the application of Al₂O₃ nanofluid as lubricant for steel hot rolling could synchronously achieve oxidation protection of strips surface. The underlying mechanism was investigated through hot rolling tests and molecular dynamics (MD) simulations. The employment of Al₂O₃ nanoparticles contributed to significant enhancement in the lubrication performance of lubricant. The rolled strip exhibited the best surface topography that the roughness reached lowest with the sparsest surface defects. Besides, the oxide scale generated on steel surface was also thinner, and the ratio of Fe₂O₃ among various iron oxides became lower. It was revealed the above oxidation protection effect of Al₂O₃ nanofluid was attributed to the deposition of nanoparticles on metal surface during hot rolling. A protective layer in the thickness of about 193 nm was formed to prevent the direct contact between steel matrix and atmosphere, which was mainly composed of Al₂O₃ and sintered organic molecules. MD simulations confirmed the diffusion of O₂ and H₂O could be blocked by the Al₂O₃ layer through physical absorption and penetration barrier effect.