Abstract: The microstructure observation, electrochemical test, immersion test and electrochemical impedance spectroscopy（EIS） test of the low alloy steel and copper-containing low alloy steel were carried out, and the microstructure,polarization property, the morphology and composition of the corrosion products after immersion test of the two steels were compared and analyzed. The influence mechanism of Cu alloying on the corrosion resistance and protectiveness of corrosion products of low alloy steel under simulated saline alkali environment（saturated Ca（OH）₂ solution containing Cl） was systematically investigated. The results show that the addition of Cu increases the corrosion potential and passivation potential of low alloy steel in the environment, and reduces the passivation current density. The corrosion products of low alloy steel with Cu alloying after immersion exhibit a denser morphology and higher content of stable corrosion products, which increases the protective properties of corrosion products and results in a decrease in pit depth. The addition of Cu promotes an increase in the capacitance arc radius and low-frequency modulus |Z|_0.01of the sample, which is related to the increase of the stable Fe₂O₃ phase content in the rust layer.