The effects of salinity on osmoregulation, gill Na⁺/K⁺-ATPase activity, gene expression, and oxygen consumption rate of juvenile hybrid grouper () were studied. In experiment 1, juvenile hybrid groupers with average weight of (162.5±12.1) g were exposed to different salinities (6, 12, 18, 24, 30) for 10 days. Serum osmolality and ion (Na⁺, Cl^‒, and K⁺) concentrations were determined. The results showed that serum osmolality and Na⁺, Cl^‒, and K⁺ concentrations increased with increasing salinity. Serum osmolality and Na⁺ and Cl^‒ from salinity group 6 were significantly lower than those of the control group (]:[Cl^‒] ratio between the groups (>0.05). The isosmotic point was calculated as 365.95 mOsm/kg, corresponding to the osmolality of the ambient water at a salinity of 12.75. In experiment 2, juvenile hybrid groupers with average weight of (26.4±2.7) g were reared at different salinities (6, 12, 18, 24, 30) for 30 d, and the activity and expression of gill Na⁺/K⁺-ATPase were measured at 0 h, 3 h, 24 h, and 72 h, as well as the oxygen consumption rate at 30 d. The results showed that the activity change curve of gill Na⁺/K⁺-ATPase was U-shaped as salinity increased, and at 3 h, the activity was significantly the lowest at salinity 18 and 24 (<0.05). After 24 h and 72 h, the activity of salinity 12 was significantly lower than all other groups ( gene fluctuated greatly, beginning with a decrease and then increasing after 72 h, which was consistent with the enzyme activity. Gene expression in salinity 12 group was significantly lower than that in the other groups (<0.05). With increasing salinity, the oxygen consumption rate initially decreased, followed by an increase, and then again a decrease. Oxygen consumption was highest in salinity group 6 and was significantly higher than that in salinity groups 12, 18, and 30 (<0.05). Our findings indicate that the juvenile hybrid grouper can adapt to 6-30 salinity changes well. Near the isosmotic point, Na⁺/K⁺-ATPase activity, oxygen consumption rate, and the relative expression of gill were lower, suggesting that growth was more favorable near this point. However, the activity of Na⁺/K⁺-ATPase was not completely consistent with the oxygen consumption rate in the experiment, indicating the oxygen consumption rate may be related to its life history stage except for regulation of ion permeability.