Abstract: Dissolved oxygen is a crucial environmental factor that significantly influences the survival, growth, and development of aquatic organisms. Fish species are diverse, and their physiological responses to hypoxic stress vary considerably. To investigate the impact of hypoxic stress on the antioxidant capacity, energy metabolism, and tissue morphology of Oplegnathus punctatus, a valuable species for deep-sea aquaculture, this study examined alterations in hepatic antioxidant enzyme activities, glycolipid metabolite levels, and tissue morphology in two size groups (200 g and 50 g) of O. punctatus under critical oxygen partial pressure (P_crit) and loss of equilibrium (LOE) conditions. The results revealed that under hypoxic stress reaching LOE, the activities of lactate dehydrogenase (LDH), pyruvate kinase (PK), phosphofructokinase (PFK), and hexokinase (HK), as well as lactate content, significantly increased (P<0.05) in both size groups, with the 200 g group showing greater increases in energy metabolism enzyme activities compared to the 50 g group. Hepatic glycogen content decreased during hypoxia, with a significant reduction in the 50 g group at LOE (P<0.05), while the 200 g group showed no significant change. Concurrently, the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) in the liver were significantly elevated (P<0.05), while malondialdehyde (MDA) content also increased significantly (P<0.05), reflecting heightened oxidative stress levels. Notably, the 50 g group exhibited smaller increases in antioxidant enzyme activities compared to the 200 g group. In contrast, the activities of lipoprotein lipase (LPL) and fatty acid synthase (FAS) showed no significant changes during hypoxia (P>0.05). Furthermore, the proportions of hepatocyte migration, lysis, and pyknosis significantly increased in both size groups, whereas the proportion of normal hepatocytes gradually decreased. All measured parameters returned to control levels 24 hours after restoration of normal dissolved oxygen. In conclusion, hypoxic stress significantly affected the glycolysis, hepatic antioxidant capacity, and tissue morphology of O. punctatus in this experiment. The fish primarily relied on anaerobic glycolysis to meet energy demands under hypoxic conditions, with the 200 g group exhibiting more pronounced changes compared to the 50 g group. These results provide a theoretical foundation and data support for the effectively management of O. punctatus in captivity.