In this study, the F 1line reciprocally crossed Taiwan red Nile tilapia(Oreochromis spp. )strain TsRn with the marine tilapia ( Oreochromis spirulus) strain, TsRn♀×TFS♂ and TFS♀×TsRn♂. One of them TsRn♀×TFS♂ got poor adaptability marine environment and die in succession. The other TFS♀×TsRn♂ had salt tolerance the same as TFS. Compare F2 , F3 , and F1(TFS♀×TsRn♂) back crossed with parents TsRn♀, TsRn♂, TFS♀ and TFS♂ to produce BC1F1, respectively. The salt tolerance of F2 3-month-old progeny survival rate was 86% (3378/3939), and there were three color types: black dots, spots and black groups. Only the black group TFS♀×TsRn♂ produced F3 3-month-old progeny survival rate was 90% (536/592). The BC1F1(TFS/TsRn♀×TFS♂) and (TFS/TsRn♂×TFS♀) have progeny, all the fry are black, and 3-month-old survival rate of (TFS/TsRn♀×TFS♂) was 78% (559/713); (TFS/TsRn♂×TFS♀) was 81% (636/785); the other cross (TFS/TsRn♂×TsRn♀; TFS/TsRn♀×TsRn♂ ) can't reproduce in marine environment. The results show that the marine adaptation trait comes from TFS, and if it was lower than 1/2 TFS descent, the salt tolerance was a problem.