To study the effects of RRR-α-tocopherol succinate on performance, antioxidant and immune function of broilers fed different oil diets, six hundred AA broilers were randomly divided into 10 treatments with 6 replicates and 10 broilers in each replicate. The experiment using a 2×5 factorial design: the oil types (fresh and oxidized oil) × α-tocopherol treatments (30 mg/kg all-rac-α-tocopherol acetate (TOA1), 30 mg/kg RRR-α-tocopherol acetate (TOA2), 15, 30, and 60 mg/kg RRR-α-tocopherol succinate (TOS1, TOS2, TOS3), respectively). The experiment lasted for 42 days. The results showed that: 1) α-TOS and oxidized oil had no significant effect on the growth performance (P>0.05) except the feed gain ratio of 1～21 day-old broilers; 2) by the amount of α-TOS increasing, the T3 and TSH levels in serum were increased and cortisol was significantly reduced, antioxidant capacity of serum was increased to some extent (P<0.05 or P<0.01), malonaldehyde (MDA) levels were significantly reduced and the Newcastle disease antibody titer were improved (P<0.05); 3) compared with fresh oil diet groups, adding with the same level α-TOS, oxidized oil made serum hormone levels, antioxidant enzyme activity and Newcastle disease antibody titers decreased, but the differences were not significant (P>0.05). These results indicated that oxidized oil diet can provoke immune stress, leading the growth performance of broilers reduced, the antioxidant decreased. α-TOS supplementation in diet can improve the broiler growth performance in a certain extent, antioxidant indices and immune function of serum，and the best group is the 60 mg/kg dietary D-α-TOS supplementation in different oil diets.［Chinese Journal of Animal Nutrition, 2010，22（3）:653-661］