Effects of variations of temperature，humidity and dehydration rate on membrane lipid peroxidation of tobacco leaves during baking time were investigated，using three varieties of flue-cured toacco，Yunyan85，K326，HD as materials．Results showed that changes in contents of leaf moisture was closely related to decrease of relative humidity in the barn．HD tobacco was more sensitive to changes of temperature and humidity in the barn compared to Yunyan85，K326 expressed in its higher dehydration rate．Cellular leaf dehydration rate directly led to the increase of severe membrane lipid peroxidation and contents of MDA．In the process of baking，activity of peroxidase was directly affected by the temperature in the barn，as well as the crease of malondialdehyde concentrations and other inhibitors caused by celluar membrane peroxidation malondialdehyde can be used as a compound landmark to indicate leaf dehydration rate and degree of damage to cellular membrane structure.