Abstract: The objective of this study was to investigate the developmental characteristics of gastrointestinal tract in confined raising lambs with supplementary feed from the age of 7 days. Forty-five male lambs (Gansu modern breeding sheep group) were divided into 9 treatments (5 animals in every treatment), which were slaughtered and sampled at the age of 0, 7, 14, 21, 28, 35, 42, 49, 56 days, respectively. The relative weight of compartments in stomach (%live weight, %stomach weight), relative capacity of compartments in stomach (%gastrointestinal tract capacity, %stomach capacity), and relative weight of compartments in intestine (%live weight, %intestinal weight) were measured. The results showed that the relative weight of stomach (% live weight, RWS-L) at 0 d was about 1% of the live weight. RWS-L at 56 d was 2.33 times as large as that at 0 d. At the same time, declines were observed in RWA-L of lambs, and RWA-L at 56 d was 79.86% as large as that at 0 d. RCF-G and RCF-S were notably increasing after 7 d, and it could be appeared that RCF-S was exceed than RWF-S at 28 d. RCA-G and RCA-S were significantly decline during 7 to 28 d. With the age in days increasing, there were some increasing in relative intestinal weight (%live weight), and it was 1.43 times at 56 d as large as that at 0 d. The growing speed of large intestine (% intestinal weight) were more quickly than that of small intestine, and the large intestine and small intestine were 1.71 and 1.36 times at 56 d as large as that at 0 d, respectively. There was more growing speed in ileum than other compartments in small intestine, but almost similar growing speeds were found in every compartment (cecum, colon, rectum) of large intestine. These results indicated that different growing speeds were appeared in gastrointestinal organs at the age of 056 d in lambs. The growing speeds of relative weight in stomach were more than that in intestine. And 7 to 14 days would be ahead on the development of weight and capacity in stomach for confined raising lambs and providing enough supplementary feed from 7 d after birth. With confined raising and supplying the suited supplementary diet, the feasible weaned age in days was 35 or 28 d after birth in lambs.