Abstract: In order to clarify the mechanism of tobacco color change during the air-curing process, the upper leaves of Dexue NO.7 were used as the experimental materials to study the changes of color parameters (L^*, a^*, b^*, C, H°, H), moisture (moisture content, water activity), membrane lipid peroxidation degree (O₂·^-, H₂O₂, MDA) and antioxidant enzyme (SOD, POD, APX) activities. The results showed that the change trend of the color parameters of the front and back of the tobacco leaves was the same during the process. During the air-curing process, the moisture in the tobacco leaves gradually lost, and the moisture loss rate in the main vein was lower than that in the leaves. The contents of active oxygen (O₂·^-, H₂O₂) and MDA increased gradually. The activities of antioxidant enzymes changed a lot, but the change rules of enzyme activities were slightly different:the activities of SOD and POD increased first then decreased, but the activity of APX decreased all the time. Correlation analysis showed that the correlations between moisture index, membrane lipid oxidation degree, antioxidant enzyme activities and color parameters were good.