This experiment was conducted to study the effects of alanyl-glutamine (Ala-Gln) alleviate oxidative damage induced by Diquat of weaned piglets. The method of double-factor design is adopted. Twenty four piglets with health condition and similar parity weaned at 21 days of age were randomly divided into 2 groups with 12 replicates in each group and 1 pig in each replicate. Pigs in two groups were fed control diet and control diet+0.30% Ala-Gln, respectively. After 7 days pre feeding, based on the prophase feeding, the 24 piglets were randomly divided into 4 groups with 6 replicates in each group and 1 pig in each replicate. The four groups were basal diet group, basal diet+0.3% Ala-Gln group, basal diet stress group and basal diet+0.3% Ala-Gln stress group, respectively. Piglet oxidative stress was simulated by intraperitoneal injection of 8 mg/kg BW Diquat, and the unstressed groups were injected with the same volume of sterilized saline. The experiment lasted for 7 days. The results showed as follows:1) piglets under oxidative stress state, compare with the basal diet stress group, dietary supplemented with Ala-Gln significantly increased the contents of glutamine (Gln), glutathione (GSH) and activities of glutathione peroxidase (GSH-Px), total superoxide dismutase (T-SOD) and total antioxidant capacity (T-AOC) in serum (P<0.05). 2) Piglets under normal physiological state and oxidative stress state, compared with corresponding basal diet group and basal diet stress group, dietary supplemented with Ala-Gln significantly increased the GSH-Px activity and T-AOC in jejunum (P<0.05), and significantly decreased the malondialdehyde (MDA) content (P<0.05); dietary supplemented with Ala-Gln significantly increased the GSH-Px activity and T-AOC in liver (P<0.05), and significantly decreased the malondialdehyde (MDA) content (P<0.05). 3) Piglets under oxidative stress state, compare with the basal diet stress group, dietary supplemented with Ala-Gln significantly increased the liver glutathione peroxidase 4 (GPx4) mRNA expression (P<0.05), and significantly decreased the superoxide dismutase 1 (SOD1) mRNA expression (P<0.05). These findings indicate that piglets under normal physiological state and oxidative stress state, diets supplemented with Ala-Gln can improve antioxidant capacity and decrease MDA content of piglets, and to alleviate the organism tissue damage of oxidative stress of weaned piglets, especially under oxidative stress state.