The exfoliation morphologies and electrochemical impedance spectroscopy (EIS) features of as received rolled AA8090 Al Li alloy in EXCO solution were studied. The EIS was simulated using an equivalent circuit. The results show that once the exfoliation occurs, the EIS is composed of two capacitive arcs at high frequency and mediate low frequency; among them, the capacitance corresponding to high frequency ( C 1) is originated from original flat alloy surface, while the capacitance corresponding to mediate low frequency ( C 2) from new interface exposed to EXCO solution due to the exfoliation and the ratio of C 2 to C 1 increases with exfoliation degree. It is advanced that the exfoliation degree can be quantitatively judged through this ratio. The exfoliation of morphologies and electrochemical impedance spectroscopy (EIS) features of as received rolled AA8090 Al Li alloy in EXCO solution were studied. The results show that once the exfoliation occurs, the EIS is composed of two capacitances arcs at high frequency and mediate low frequency; among them, the capacitance corresponding to high frequency (C 1) is originated from original flat alloy surface, while the capacitance corresponding to mediate low frequency (C 2) from new interface exposed to EXCO solution due to the exfoliation and the ratio of C 2 to C 1 increases with exfoliation degree. It is advanced that the exfoliation degree can be quantitatively verified through this ratio.