Abstract: Four enzymes(protease,cellulase,amylase and sucrase) in Yunnan flue-cured tobacco cv.K326 of different grades sampled at different intervals during aging were examined.The results showed that the activities of protease,amylase,cellulase and sucrase ranged from 4.3 U to 10.3 U,1.7 U to 4.2 U,7.7 U to 18.7 U,and 0.8 U to 3.8 U,respectively.The activities of the enzymes were significantly influenced by aging duration and decreased with the proceeding of aging.Meanwhile,the enzyme activity was significantly correlated with leaf position and grade,it was stronger in cutters than in upper and lower leaves,however,there was no obvious difference between upper and lower leaves.