Abstract: The mechanism of corrosion-inhibiting action of ethoxylated rosin amine was investigated by measuring the corrosion rates with gravimetric method. The analysis of the kinetics of steel in HC1 solution and the characteristic relationship between the inhibiting efficiency and temperature suggete that chemisorption is the mechanism of inhibiting action of ethoxylated rosin amine (RAO). It has been found that RAO is adsorbed according to Langmuir and non-Langmuir isotherm when the temperature below 40℃ and above 60℃, Polarization measurements indicate that RAO is a strong cathodic inhibitor which inhibits cathodic process of the electrode.