Effects of supplementation selenomethionine on performance, selenium concentrations and antioxidative indices in serum and milk in sows were studied. A total of 12 healthy sows (Landrace×Yorkshire) which were in the late period of pregnancy with the same parity, were randomly allocated into 2 treatments of 6 replicates of 1 sow. The control group received the basal diet (content of selenium was 0.04 mg/kg) supplemented with 0.3 mg/kg Se in form of sodium selenite (SS), and 0.3 mg/kg Se in form of DL-selenomethionine (DL-SeMet) was added to the basal diet for the experimental group. The total test period lasted for 60 d, including 32 d of prepartum and 28 d of lactation. Results showed that compared with SS group, the weanling litter weight, weanling individual weight and milking capacity in DL-SeMet group were significantly increased by 8.00% (P<0.05), 9.78% (P<0.05) and 9.95% (P<0.05), respectively. Serum T-AOC level was significantly increased (P<0.05) while MDA level was decreased (P<0.01) in serum of sows. In colostrum and milk on day 7, 14, 21 and 28, T-AOC level and GSH-Px activities were significantly increased (P<0.05) while the MDA level was decreased (P<0.05). Selenium content in serum and milk were significantly increased (P<0.05). These results suggested that DL-SeMet contributed to improving milk Se content and antioxidative capability in serum and milk of sows, and promoting the growth of nursing pigs.［Chinese Journal of Animal Nutrition, 2009，21(6):910-915］