To investigate the influence of sodium to potassium(Na/K) ratios on the growth performance and physiological response of the Pacific white shrimp( Litopenaeus vananmei), various concentrations of KCl were added to low-salinity well water(salinity 4) in an 8-week culture trial. Six treatments with Na/K ratios of 60:1, 42:1, 33:1, 23:1, 17:1, and 14:1 were replicated in triplicate. The highest weight-gain rate(3 506±48)% and survival rate(89.38±0.88)% was observed in well water with Na/K ratios of 23:1 and 42:1, respectively, while the feed conversion ratio(1.02±0.01), oxygen consumption, and ammonia-N excretion rate was the lowest in the medium with a Na/K ratio of 23:1. Gill Na +-K +-ATPase activity, as an indicator of osmoregulation, peaked in the treatment where the Na/K ratio was 17:1. The total hemocyte count, respiratory burst, and immune-related enzyme activities(ALP, LSZ, PO, and SOD) of L. vananmei were affected significantly by Na/K ratios( P <0.05). After challenged with Vibrio harveyi, the cumulative mortality of shrimp reared in a Na/K ratio of 23:1(30±14.14)% was significantly lower than the control(75±7.07)%. In conclusion, the addition of K + to low-salinity well water in L. vannamei cultures is feasible. Na/K ratios ranging from 23:1 to 33:1 might improve survival and growth. Immunity and disease resistance are also closely related to the Na/K ratio of the low-salinity well water. The findings may contribute to the development of more efficient K + remediation strategies for L. vananmei culture in low-salinity well water. To investigate the influence of sodium to potassium (Na / K) ratios on the growth performance and physiological response of the Pacific white shrimp (Litopenaeus vananmei), various concentrations of KCl were added to low-salinity well water (salinity 4) in an 8 -week culture trial. Six treatments with Na / K ratios of 60: 1, 42: 1, 33: 1, 23: 1, 17: 1, and 14: 1 were replicated in triplicate. The highest weight-gain rate 506 ± 48% and survival rate (89.38 ± 0.88)% were observed in well water with Na / K ratios of 23: 1 and 42: 1, respectively, while the feed conversion ratio (1.02 ± 0.01) ammonia-N excretion rate was the lowest in the medium with a Na / K ratio of 23: 1. Gill Na + -K + -ATPase activity, as an indicator of osmoregulation, peaked in the treatment where the Na / K ratio was 17 : 1. The total hemocyte count, respiratory burst, and immune-related enzyme activities (ALP, LSZ, PO, and SOD) of L. vananmei were significantly affected by Na / K ratios (P <0.05) ibrio harveyi, the cumulative mortality of shrimp reared in a Na / K ratio of 23: 1 (30 ± 14.14)% was significantly lower than the control (75 ± 7.07)%. In conclusion, the addition of K + to low-salinity Immunity and disease resistance are also closely related to the Na / K ratio of the low-salinity well water The findings may contribute to the development of more efficient K + remediation strategies for L. vananmei culture in low-salinity well water.