Chlorine dioxide (ClO2), recognized for its high efficiency, broad-spectrum capabilities, and safety, is extensively utilized in water disinfection processes. Possessing strong oxidizing properties, prolonged exposure to ClO2 can lead to irreversible corrosion of metals. To mitigate the ClO2-induced corrosion on steel, the corrosion inhibition performance and underlying mechanism of BMIMAc and BMIMBr on 20 steel and Q235 steel in ClO2 solutions ranging from 2.5 to 10 mg/L is systematically studied by static weightlessness experiments, potentiodynamic polarization curve experiments, SEM, EDS, DFT calculations, and MD simulation. The findings demonstrate that both ionic liquids significantly impede corrosion, where BMIMAc outperforms BMIMBr in terms of corrosion inhibition efficacy. These inhibitors exhibit effective adsorption onto the carbon steel surface, conforming to the Langmuir isotherm model. Both ionic liquids are cathodic inhibitors. They can adsorb on the metal surface in an approximately parallel manner and their imidazole ring can form a coordination bond with the metal, leading to the formation of an adsorbent membrane that prevents further contact of the metal with ClO2, thus reducing the degree of oxidation and retarding the corrosion process.