Conventional lubricants such as emulsions and oils used in cold rolling often result in poor surface cleanliness and raise environmental concerns related to waste disposal. Water-based nanofluids have emerged as promising alternatives owing to their high cooling efficiency, environmental compatibility, and cost-effectiveness. However, the use of Cu nanofluids for cold rolling lubrication, and the underlying tribochemical mechanisms, remain insufficiently understood. In this study, stable water-based Cu nanofluids were prepared and applied to cold rolling. Experiments demonstrated that 0.3 wt% Cu nanofluid provided optimal lubrication, yielding the lowest rolling force, a total thickness reduction of 81.8 %, and a minimum surface roughness ( R a) of 0.325 μm. A tribofilm with a thickness of 30–58 nm was generated at the friction interface through tribochemical reactions, comprising CuO, Cu 2O, Fe 2O 3, Fe(OH)O, and FeCu 4. Molecular dynamic simulations further revealed the adsorption and diffusion behaviors of Cu atoms and O 2 molecules on Fe slabs at the atomic scale. Meanwhile, Cu nanoparticles exhibited synergistic sliding, rolling, and polishing effects, which together enhanced lubrication performance.