Abstract: The trial was combined with a feeding experiment, in which twentyfour three-way cross-bred lambs(Poll Dorset♂×Small Tailed Han×Tan♀, averaged at 35.5 days old) were divided into three groups and each with eight lambs(♂1,♀7)，pen-fed singly. The experiment lasted sixty-five days including 15 days for the preliminary period. Lambs were fed with three diets at different levels of digestible energy(DE) and crude protein (CP),i.e.I- 0.9NRC,II- 1.0NRC and Ⅲ-1.1NRC， respectively, during the recording period of 50 days.Sampling of the digestion trial using five female lambs for each group were made from the days 21 to 26 during the recording period, and four lambs(♀) in each group were slaughtered at the end of the feeding experiment to study the digestion of these diets and the development of alimentary tract for lambs. The results showed that the apparent digestibility of dry matter, organic matter, crude protein and acid detergent fiber（DMD, OMD, CPD,ADFD） increased with the raising of nutrition level in diets. DMD and OMD were higher for diet Ⅲ than that for Ⅰ（P＜0.01）and Ⅱ（P＜0.05）; CPD from Ⅲ was higher than that from Ⅰ and Ⅱ（P＜0.01）, DMD of Ⅱ was higher than that of Ⅰ（P＜0.05）.The ADFD of Ⅰ was lower than that of Ⅲ（P＜0.01）. The changes of apparent digestibility of calcium and phosphorus (CaD ,PD) were not regular as nutrition levels. The weight of alimentary tract(% of lifeweight before slaughtering) and the weight of each compartment of stomach(% weight of whole stomach) were not affected by nutrition levels（P＞0.05）. The weight of rumenreticulum(% weight of whole stomach) for the lambs of all groups had reached the levels of adult sheep.