Corrosion inhibition effect of N(4sulfonic acid) butyl triethylammonium hydrogen sulfate((CH2)4SO3HTEA\]\[HSO4]) acid ionic liquid(IL) towards Q235 steel corrosion in 0.5 mol/L HCl solution was investigated by electrochemical measurements in 25 ℃. The results show that the IL suppressed corrosion processes of Q235 steel in HCl solutionand the best performance of inhibition could be obtained with the concentration of inhibitor 14 mmol/L. The X-ray photoelectron spectroscopy(XPS) demonstrates that the protectiue film is formed by adsorption on the Q235steel surface, which can cover the reative center and inhibit the Q235 steel corrosion in HCl solution.