The biochemical characteristics has been defined from 7 strains of A. hydrophila isolated from infected fish in Red river delta show typical of species that is motion, fermentation of glucose and lactose, H2S, indol and gas producing, catalase positive, gelatinase-positive, anpha and beta haemolytic type. Two of the seven A. hydrophila strains named C5 and C8 are used to study the adaptive characteristics showed that both of selected bacterial strains are preferred warm, time and temperature most suitable for growth respectively 36 hour and 28°C, at temperatures range between 18-37oC, haemolytic toxin can be produced after 20 culture hours. A. hydrophila able to grow well in acidification, eutrophication and neutral water environment. For salinity tolerance, A. hydrophila can be growth well at salt concentration of 0.5 percent but at 11.5 percent of salt concentration, selected of A. hydrophila can cause disease in fish. Regarding antibiotic resistance, seven Ahydrophila strains were resistant or not susceptible to erythromycin and neomycin.