Abstract: In the trial,the effects of organic selenium source on lamb′s growth performance and antixidative activities were investigated. 30 lambs with body weight of 20 kg were randomly divided into three groups,the control group wasn＇t supplemented any selenium,but selenium-enriched yeast and sodium selenite respectively was added up to two test groups at the dosage of 0.1 mg/kg. The results indicated that selenium-enriched yeast couldn′t improve lamb′s growth performance. At 30 and 60 day ages,superoxidedismutase （SOD）activity and GPx activity in the two test group both were higher than that of the control group,the difference was significant （P〈 0.05）,but malonaldehyde （MDA） level of serum was lower than that of control with marked difference （P 〈0.01）. In conclusion,antixidative activities of organic selenium were better than that of inorganic selenium.