Abstract: 【Objective】The salinity and alkalinity tolerance of the third, fourth and fifth generation (F3, F4 and F5) of Nile tilapia (Oreochromis niloticus) was evaluated in order to provide basic data for the salinity and alkalinity breeding of Nile tilapia.【Method】The acute lethal test method was used to determine the tolerance of salt, alkali (NaHCO3) andsalinityalkalinity to the F3, F4 and F5 generation of Nile tilapia. 【Result】The results showed that under the acute lethal condition, the semi-lethal concentrations of 96h salinity of F3, F4 and F5 generations were 22.473 g/L, 24.468 g/L and 23.833 g/L, respectively; while the semi-lethal concentrations of 96h alkalinity were 8.256 g/L, 8.443 g/L and 8.453 g/L, respectively. In the salinity-alkalinity experiment, when the salinity was 10 g/L, there was no death. When the salinity was 15 g/L, the semilethal concentrations of 96 h alkalinity were 4.612 g/L, 4.538 g/L and 4.83 g/L, respectively. When the salinity was 20 g/L, the semi-lethal concentrations of 96 h alkalinity were 1.861 g/L, 1.875g/L and 1.782 g/L, respectively. Under the acute test, there was no significant difference between F4 and F5 selected generations in semi-lethal concentrations of salinity, alkalinity and salinity-alkalinity. Under the acute salinity test, salinity semi-lethal concentrations of F4 and F5 were significantly higher than those of F3 .Under the acute alkalinity test and the salinity-alkalinity test, the semi-lethal concentrations of F4 and F5 were not significantly different from those of F3 .【Conclusion】The results showed that the salt and alkali tolerance of F5 selected generation of Nile tilapia was stable.