Abstract: The effects of the activity of amylase and starch phosphorylase on the starch degradation in tobacco leaves of different maturity were studied by using the cutters of flue-cured tobacco cv. HD and K326 as experimental material. The results indicated that starch degradation was the result of synergism of amylase and starch phosphorylase. There were two peaks of amylase activity, at the 36th and the 72nd hours during curing, respectively. The activity of starch phosphorylase was relatively higher in fresh leaves. With the proceeding of curing, the activity of starch phosphorylase reached its first peak at the 24th hour, followed by a valley at the 48th hour, and then the second peak at the 72nd hour. The activity of the two kinds of enzymes was relatively higher, starch degradation was relatively quicker in ripe leaves. The content of starch was lower, while the contents of soluble sugar and reducing sugar were higher and the whole of chemical components was relatively harmonious in ripe leaves after flue-curing.