Abstract: The 48 healthy rams of Small Tailed Han sheep with approximate weight were divided into 4 groups. Every group was fed with the basal diet containing 0, 75, 150 and 22.5 mg cysteamine/kgBW respectively. The effects on activities of amylase, trypsin and chymotrypsin in the digesta of small intestine were studied by the experiment with different levels of cysteamine in the diet of sheep. The results indicated that the activities of amylase, trypsin and chymotrypsin in different parts(duodenum, jejunum and ileum) of the small intestine were not the same . The activities of the three digestive enzymes in jejunum were significantly higher than that in duodenum and ileum. With the content of cysteamine increased in the diet, the activities of amylase, trypsin and chymotrypsin increased either, but when the content of cysteamine reached certain level(22.5 mg/kgBW), the activities of amylase, trypsin and chymotrypsin decreased instead. Therefore, it is necessary for selecting proper content of cysteamine in diets of sheep.