Abstract: Corrosion rank of high strength aluminum alloy in aircraft by visional inspection is a qualitative but simple method,while the most reliable parameter that reflects the corrosion of aluminum is the maximum corrosion depth.In order to make corrosion rank more reliable, corrosion rank and maximum corrosion depth of two high strength aluminum alloys (LY12CZ and 7075T7351) in EXCO solution was measured.At each corrosion rank,a number of corrosion depth data were obtained.With the statistic analysis, the relationship between the rank and the depth was established.So,corrosion rank of LY12CZ and 7075T7351 aluminum alloy in EXCO solution was half-quantified. By determining corrosion rank, the maximum corrosion depth of LY12CZ and 7075T7351 aluminum alloy can be evaluated approximately.