This experiment was conducted to investigate the effects of supplemental level of concentrate on complex stomach development of early-weaned lambs. Thirty-two (35±3) days old lambs with an average body weight of (8.58±1.83) kg were randomly divided into 4 groups with 8 lambs in each group (half male and half female), and each lamb was fed in an individual pen. Lambs in control group were fed by ewes, and lambs in experimental groups were weaned at 35-day-old and fed diet supplemented with 50, 150 and 250 g/d concentrate, respectively. The experiment lasted for 42 days. The results showed as follows: concentrate supplementation could increase the ratio of complex stomach weight to body weight (P<0.01), the weight gain of abomasums (P<0.05) and rumen papillae width (P<0.01), and decrease rumen papillae density (P<0.05). The effects of concentrate supplementation on the above indices were increased with the concentrate level increasing. Concentrate supplementation had no effects on rumen wall thickness and papillae length (P>0.05). In conclusion, concentrate supplementation can promote the complex stomach development of early-weaned lambs, and the optimum level is 250 g/d.［Chinese Journal of Animal Nutrition, 2010，22（6）:1757-1761］