Objective To study the inhibition effect of thiourea on corrosion of Non-quenched and tempered steel in HCl solution. Methods The polarization curves and electrochemical impedance were measured by electrochemical workstation. The corrosion morphology of Non-quenched and tempered steel was observed by three-dimensional video microscope. Results The corrosion potential of non-quenched and tempered steel in HCl solution without corrosion inhibitor was ?0.566 V, and the corrosion current density was 12.57 mA/cm2.With increasing concentration of thiourea in HCl solution, the corrosion current density of Non-quenched and tempered steel gradually decreased, the interfacial electric double layer capacitor (Cdl) gradually decreased, the reaction resistance and inhibition efficiency gradually increased, the cathodic polarization curves almost coincided and the anodic polarization curves gradually shifted positively. When the concentration of thiourea was 5 g/L in HCl cleaning solution, the corrosion inhibition efficiency reached up to 91.17%. The corrosion inhibition effect of thioureai was better than that of the commercial inhibitor AS-30. Thiourea could eliminate the emerging of pitting in HCl solution. Conclusion Thiourea had obvious inhibition effect for non-quenched and tempered steel in HCl solution and could effectively eliminate the corrosion pitting.