This experiment was conducted to investigate the growth performance, slaughter performance and organ indexes of Dorper譙mall Tail Han sheep crossbred male lambs from 20 to 35 kg of live weight. Twenty-one lambs were randomly assigned to three groups with one group fed ad libitum (AL group), and the other two groups fed either 70% (IR70 group) or 40% (IR40 group) of ad libitum. A slaughter trial was performed after the lambs in the AL group reached 35 kg of live weight. The experiment lasted for 66 d. The results showed as follows: different feeding levels had significant effects on net gain, average daily gain and dry matter intake, and partial slaughter indexes among three groups (AL>IR70>IR40) (P<0.05); no significant differences were found in dressing percentage, net meat percentage and net meat percentage of carcass among three groups (P>0.05); in the AL group, the ratio of rumen weight to total complex stomach weight was the highest (67.08%) and no obvious difference was found between AL group and IR70 group (P>0.05). Besides, the ratio of liver weight to live weight in the AL group was higher than that in the other two groups (P<0.05). The results indicate that feeding level has different effects on growth performance, weight and development of complex stomach and other main organs of mutton sheep. Results of growth, slaughter performance and organ indexes of Dorper譙mall Tail Han sheep crossbred male lambs are different from the data reported by NRC (2007).