The inhibition effects of sodium lignosulphonate (SLS) have been studied by means of weight loss method, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The results showed that sodium lignosulphonate (SLS) could inhibit effectively the corrosion for AZ31 magnesium alloy in 3.5% NaCl solution, and that the consisting of 4.0 g/L SLS is of an inhibition efficiency higher to 75.4%. SLS is an anion inhibitor and the adsorption of SLS on the AZ31 magnesium alloy surface obeys to the Langmuir adsorption isotherm which due to the adsorption free energy ?G0 and the Arrhenius active energy Ea.