Abstract: In order to assess the salinity-alkalinity tolerance and growth performance of the 3rd selected generation of Nile tilapia Oreochromis niloticus，chronic salinity-alkalinity lethal test was carried out for the 3rd selected generation of tilapia fingerling and the control group in tanks of 0.6 m× 0.4 m × 0.5 m. And 60 days growth trail were carried out in cement tanks of each 6.0 m×5.0 m×1.6 m for the 3rd selected generation and the five control groups reared in fresh water（ S0A0 group） ，salinity group（ 10 g/L，S10A0 group） and different salinity-alkalinity waters（ 10，2） g/L，S10A2 group；（10，4） g/L，S10A4 group；and（ 10，6） g/L，S10A6 group. It was found that the median lethal salinity was 39.63（±2.12） g/L for the 3rd selected generation，and 31.42（±2.42） g/L for the control group，and the median lethal alkalinity was 13.94（±0.25） g/L for the 3rd selected generation and 11.26（±0.15） g/L for the control group. The average growth rate of the 3rd generation and control group decreased in S10A0，S10A2， S10A4 and S10A6 groups with the elevation of alkalinity. Uder the same salinity-alkalinity condition，the average growth rate of the 3rd selected generation group was significantly higher than that of control group.