The corrosion inhibition of calcium lignosulfonate (CLS) for Q235 carbon steel in saturatedCa(OH) 2 +0.1 mol/L NaCl solution was studied by means of weight loss, polarization, fluorescence microscopy(FM), scanning electron microscopy/energy dispersive spectrometry (SEM/EDS), microscopic infrared spectral imaging (M-IR) and X-ray photoelectron spectroscopy (XPS). For the steel in simulated concrete pore solution (pH 12.6), an increase of E b value and a decrease of i corr value occurred with different concentrations of CLS. The optimal content of CLS was 0.001 mol/L at which the inhibition rate was 98.86% and the E b value increased to 719 mV after 10 h of immersion. In mortar solution and in reinforced concrete environment, CLS also showed good inhibition for steel. The preferential adsorption of CLS around pits was detected by M-IR. The result illustrates that at the early stage the adsorption of CLS was heterogeneous and CLS may have a competitive adsorption with chloride ions at the active sites,which would be beneficial for decreasing the susceptibility of pitting corrosion. After the pre-filming time,an intact adsorption CLS film formed on carbon steel surface. The adsorption between CLS and calcium presented as Ca O S bonds. The adsorption of CLS on carbon steel surface occurred probably by both physisorption and chemisorption.