Objective To investigate the corrosion inhibition behavior of Hydroquinone(HQ) on carbon steel in 1 mol/ L HCl solution. Methods Weight-loss method, electrochemical impedance spectroscopy ( EIS) and potentiodynamic polarization techniques and scanning electron microscope (SEM) observation were used to analyze the inhibition efficiency, mechanism and corrosion appearance on steel surface when HQ was mixed with KI. Results Weight-loss results obtained indicated that the highest inhibition efficiency of Hydroquinone was only 36. 2% when was used alone; while the inhibition efficiency increased with Hydroqui- none concentrations when KI coexisted in hydrochloric acid solution and the highest inhibition efficiency could reach 81. 4% at 25 ℃. In addition, it was found that the adsorption of Hydroquinone on carbon steel obeyed the Langmuir adsorption isotherm and showed the adsorption in favor of physisorption mechanism. Potentiodynamic polarization data indicated that the inhibitor was a type of anodic effectiveness. The EIS indicated charge transfer resistance increased with HQ concentration at certain concentration of KI in HCl solution. Scanning electron microscopy observation showed HQ+KI had an obvious protective effect on metal corrosion. Conclusion Hydroquinone was an effective pickling inhibitor for C38 steel with KI.