Abstract: Four hundred and forty 1-day-old AA broiler chickens were randomly allocated to four groups for 5 replicates, and fed a commercial starter diet and the same diets supplemented with 1 000 U/kg (250 mg/kg), 3 000 U/kg (750 mg/kg), 9 000 U/kg (2 250 mg/kg) of α-amylase preparation up to 21 day of age to study the effects of supplementary αamylase of different levels on the development of digestive organs, intestinal enzyme activities. The results showed that relative weights of liver, gizzard, anterior intestine and relative length of anterior intestine tended to decrease (P>0.05).The increased activities of amylase, protease (P<0.05), and trypsin (P<0.05) in anterior intestinal and high-dose-depression responses with the amylase supplementation of 2 250 mg/kg were observed.Lipase activity, however, was unaffected by amylase supplementation of all levels (P>0.05). DNA, RNA concentration and the activities of maltase and sucrase within jejunal mucosa were not affected by supplementary amylase of 250 mg/kg and 750 mg/kg. High-dose-depression responses were also observed for the activities of maltase and sucrase (P<0.05)