This study aims to understand the effects of oxidative stress on serum biochemical indexes, energy metabolism and apparent digestibility of amino acids in terminal ileum. In the study, twelve healthy 21-day age weaned piglets (Duroc×Landrace) with an average weight of (8.10±0.89) kg were performed T cannula fit surgeon and then divided into 2 groups at random. The studied 2 groups were fed basal diets, and the body weight was weighed once a week. The treatment group was supplemented with D-galactose in the basal diet at a daily dose of 10 g/kg. We used D-galactose as a model to induce chronic oxidative stress in weaned piglets for 28 days. The results showed that, D-galactose supplementation significantly reduced the total antioxidant capacity, catalase and total superoxide dismutase activities in serum of weaned piglets, but significantly increased the concentration of malondialdehyde. Oxidative stress significantly reduced serum urea nitrogen levels in weaned piglets, while other serum biochemical indicators were not significantly different from the control group. Compared with the control group, oxidative stress significantly increased oxygen consumption, carbon dioxide production, heat production, respiratory quotient and fecal energy. Oxidative stress significantly or extremely significantly reduced the apparent digestibility of lysine, methionine, threonine, leucine and isoleucine among the terminal ileal essential amino acids, and it also significantly or extremely significantly reduced the apparent digestibility of non-essential amino acids except proline and glycine. A model of chronic oxidative stress in weaned piglets could be established using D-galactose at a dose of 10 g/kg. Chronic oxidative stress in weaned piglets not only reduced the activity of the antioxidant enzyme system and increases the level of oxidation, but also inhibited energy metabolism and terminal ileal amino acid digestion levels, which adversely affected the production of weaned piglets.