Sarotherodon melanotheron, Oreochromis niloticus, Israel red tilapia and Oreochromis aureus were used as parents which produced nine offspring by selfed and diallel crossing.After trials of lethal salt tolerance,median lethal salinity and gradual salt-tolerance domestication,differences of salt-tolerance ecological characteristics were compared and analyzed.The major results were:(1) There were greatest significant differences(P<0.01) of MST, ST₅₀ and survival rate between S.melanotheron and the other 8 tilapias,S.melanotheron’s MST was (9.24±1.353)h,ST₅₀ was (6.20±1.235)h,theoretic MLS₉₆ was 30.2,observed MLS₉₆ was 31.2,these values were far higher than those of the other 8 tilapias.(2) 9 tilapias might be divided into four groups based on their salt tolerance:the first group was S.melanotheron which had the strongest salt-tolerance among nine tilapias;the second group was Israel red tilapia and O.niloticus♀×O.aureus♂ which had strong salt-tolerance and had positive residual values;the third group was O.aureus,O.niloticus♀×Israel red tilapia ♂,Israel red tilapia♀× O.niloticus, ♂O.niloticus♀×O.aureus♂, and O.aureus♀×O.niloticus♂ which had stronger salt-tolerance and had negative residual values;the fourth group was O.niloticus which had inferior salttolerance.(3) When domesticated gradually salinity rising, S.melanotheron’s mortality rose from 0 to 30%,then it rose slowly,there was a fast rising during the fourteenth day to fifteenth day,and then it rose slow too,50%mortality occured on the eleventh day which had a 32.8 salinity,all trial fish dead on the thirtyninth day,which salinity was 102.The regress relation between mortality and domestication time of S.melanotheron was LnY=3.430+0.640X(R²=0.976).(4) S.melanotheron would be a perfect parent which bred new seed of salt tolerance.