Abstract: 240 one-day-old Avian broilers were randomly divided into 4 groups, with 60 birds in each group. Group 1 served as control, while group 2 to 4 were respectively supplemented with 0.2%, 0.4% and 0.8% glutamine (Gln) in basal diet for 28 days, and the effects of dietary Gln (glutamine) supplementation on the development of small intestine, structure and absorption functions in broilers were studied. The results indicated that dietary glutamine supplementation significantly increased the length, weight and index of small intestine of the birds in the experimental groups, and 0.8% Gln in the diet had more evident effects on the development of small intestine before 2-week-old, but 0.2% Gln supplementation was sufficient for broilers on 3 or 4-week-old. The jejunum was the first part influenced by dietary Gln, the ileum took second place and the duodenum was less affected. The histological observation indicated that villus height in jejunum was greater (P<0.05), but the villus width and the lamina depth of jejunum significantly decreased in 0.2% Gln supplemented group compared with control. The serum D-xylose detection indicated that the D-xylose concentration was greater in the Gln-supplemented groups than that of the control group during the experimental period. All the results above implied that as the main fuel for the intestinal mucosal cells under stress conditions, exogenous Gln might play an important role in facilitating the proliferation of mucosal cells, maintaining intestinal modality and improving the active absorption function.