Abstract: To investigate the effect of dissolved oxygen (DO) on the tissue structure and activities of the antioxidant enzyme in the body kidney of the Qinghai Lake scaleless carp, Gymnocypris przewalskii, with an average weight of (97.68±0.12) g, were randomly divided into three groups with moderate hypoxia (3.0±0.1) mg/L), severe hypoxia (0.7±0.1) mg/L, and normal oxygen level (8.4±0.1) mg/L for 8h and 24h. The structure of the body kidney and the ultrastructure of the body kidney mitochondria were observed, and the membrane potential of mitochondria and the activities of antioxidant enzymes were assayed. The results showed that moderate and severe hypoxia did not damage the structure of the body kidney and ultrastructure of the mitochondria. However, moderate and severe hypoxia significantly increased the ratio of renal rod mitochondria at 24h with markedly decreased membrane potential of the mitochondria. Severe hypoxia but not moderate hypoxia significantly increased the activity of SOD and the concentration of H₂O₂. Furthermore, both severe and moderate hypoxia markedly increased the concentrations of total antioxidant capacity (T-AOC), glutathione peroxidase (GPX), and malondialdehyde (MDA) in the body kidney of the scaleless carp. These results indicate that the body kidney of the scaleless carp adapt to environments via regulating mitochondrial morphology and antioxidant enzymes. This study provides a theoretical basis for understanding the hypoxia adaptation mechanism of Qinghai Lake scaleless carp.