China has abundant saline-alkaline water resources, mainly including the North China coastal composite type, Northwest sulfate type, and Northeast carbonate type, which differ in their ion composition, being mainly composed of Cl^– , SO₄ ^2–, and HCO₃ ^– . The toxic effects of saline-alkaline water on aquatic organisms are mainly caused by factors such as high ionic concentration, osmotic effect, and high pH. Simulating the saline-alkaline habitat in the laboratory has practical and guiding significance for the rational development of corresponding taming and screening schemes based on the toxic effects of different saline-alkaline water types. To investigate the toxic effects of different salts on mandarin fish (Siniperca chuatsi), acute stress tests were conducted with NaCl, Na₂SO₄, and NaHCO₃ at equal cation concentrations (Na⁺ =210 mmol/L). Blood and gill tissues were collected at 0, 12, and 24 hours after the NaCl and Na₂SO₄ stress tests, and at 24 and 72 hours after freshwater recovery. Blood and gill tissues were also collected at 0.5 hours after the NaHCO₃ stress test and at 2 and 4 hours after freshwater recovery. The serum osmotic pressure, electrolyte concentrations, and enzyme activities of Na⁺ /K⁺ -ATPase (NKA), Na⁺ /K⁺ /2Cl^– cotransporter (NKCC), Na⁺ /HCO₃ ^– cotransporter (SLC4A4), and Cl^– /HCO₃ ^– ion exchanger (SLC26A6) were analyzed. The expression levels of immune-related genes (Ccl20, γ-IFN, Dapk2) were also examined. The results showed that under 210 mmol/L Na⁺ stress, the Na⁺ concentration in the serum of the mandarin fish fluctuated significantly in all the three salt stress groups, while the changes in Cl^– and K⁺ concentration were weak. The NKA enzyme activity in gill tissues was upregulated, and the NKCC and SLC26A6 enzyme activities were inhibited. Further, γ-IFN and Dapk2 were downregulated. Unlike the fish in the NaCl and Na₂SO₄ stress test groups, the mandarin fish had a stronger stress response in the NaHCO₃ stress test group, and the serum osmotic pressure could not be restored after transferring to freshwater. The SLC4A4 enzyme activity was inhibited, and the expression levels of Ccl20 were downregulated. Therefore, the NaHCO₃ stress had a stronger toxic effect on mandarin fish than either NaCl or Na₂SO₄ stress. NaHCO₃ stress inhibited immune function and significantly inhibited the activity of most ion transporters, leading to the failure of serum osmotic regulation after being transferred to fresh water, while the osmotic regulation was functional under NaCl and Na₂SO₄ stress. The research results have practical significance for the rational development of taming and screening schemes of mandarin fish for different saline-alkaline water types.