Objective To study the effect of Cl- concentration on the corrosion behavior of 3003 aluminum alloy, and to provide reference for the corrosion test and service life assessment of the radiator. Methods The accelerated corrosion of 3003 aluminum alloy in simulated marine atmospheric environment with continuous salt spray corrosion was studied, and the microstructure, element distribution, corrosion mass loss and pitting depth of corrosion products were analyzed. The electrochemical behavior of corrosion samples was studied by polarization curve and impedance technique. Results When the Cl- concentration was lower than 9% , the mass loss of the sample increased with the increase of Cl- concentration and a maximum of 7. 9937 g/ m2 was achieved at a Cl- concentration of 9% ; the corrosion depth increased with increasing concentration of Cl- and a peak value of 44. 15 μm was reached at a Cl- concentration of 9% ; the corrosion current density increased with the increasing concentration of Cl-, while the capacitive reactance arc radius decreased with the increase of the concentration of Cl-. When the Cl- concentration was higher than 9% , the corrosion mass loss and corrosion depth continuously decreased with the increasing Cl- concentration, the current density showed a decreasing trend, and the capacitive reactance arc radius showed an increasing trend. Conclusion When Cl- concentration was in the range of 1% ~ 9% , the increasing Cl- concentration could obviously accelerate the corrosion of 3003 aluminum alloy. When the Cl- concentration was higher than 9% , the corrosion rate decreased with the increasing Cl- concentration.