Abstract: Protein and peptides are popular supplements in sports nutrition which is most often used to increase the exercise performance of human and animals. The antioxidant capacities and antifatigue properties of whey hydrolysates fermented by Lactobacillus plantarum TUST200209 and its purified whey peptides were studied. The treatment groups were orally administered with high dose (1.5 g/kg/day) and low dose (0.5 g/kg/day) of whey hydrolysates and its purified peptides in Kunming mice for four weeks, respectively. High dose (1.5 g/kg/day) of 0.9% saline (vehicle group) and mixture of whey and Lactobacillus plantarum TUST200209 were used as control. Compared with vehicle group, whey hydrolysates and its purified peptides could significantly prolong the swimming time to fatigue (p<0.05) and increase levels of superoxide dismutase and glutathione peroxidase. Moreover, contents of malondialdehyde in red cell, quadriceps femoris and mitochondria decreased and most of the changes were significant (p<0.05) for the high dose of whey peptides. The high antioxidant capacities were consistent with high antifatigue ability. Compared with vehicle group, the group oral administered high dose of whey peptides demonstrated high levels of glucose, non-esterified fatty acid and liver glycogen (p<0.05). It demonstrated that the whey hydrolysates could significantly alleviate exercise fatigue of the mice induced by free radical, especially for its purified peptides.