Abstract: The rust layer of a weathering steel was obtained by using dry-wet circle test and then analyzed by Electrochemical Impedance Spectroscopy (EIS) with an established equivalent electrical circuit. The results indicated that the technique of EIS test could be used to analyze characteristics of the inner rust layer of the weathering steel effectively. The combination of dry-wet circle test and EIS test would be applied to evaluate the weathering steel's corrosion-resistant performance rapidly and reasonably.