The dominant bacterial strain,designated as Z1,was isolated from hepatopancreas of diseased Danio rerio.The biochemical and physiological characteristics of the isolated strain was studied by using conventional method,such as ATB Expression System (ID32 STREP),16S rRNA and gyrB gene sequence.The results confirmed that the strain Z1 was Edwardsiella tarda. The challenge tests were carried out by artificially infecting D.rerio and Puntius tetrazona with the pure culture of the isolated strain.The symptoms of the artificially infected fish were similar to those infected naturally and the characters of the re-isolated strains were the same as the initially isolated strain.Antibiotic sensitivity test showed that among 17 antibiotics tested 11 were sensitive and 6 were resistant.The antibacterial activity of 15 Chinese herbs to pathogenic E.tarda (Z1) was determined in vitro by two fold dilution method.The results showed that Galla chinensis and Pericarpium granati were found to have significant inhibition on the bacterium with both minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) less than 6.25 mg/mL; Artemisiae argyi,Catsia tora,Prunus mume Sieb. et Zucc.,Pulsatilla chinensis,Coptis chinensis Franch.，Rheum palmatum L.，Scutellariae baicalensis Georgi showed some extent inhibition on the bacterium with MIC and MBC of 25-200 mg/mL,but Chrysanthemum indicum L.,Lonicera japonica,Astragalus membranaceus (Fisch.) Bge,Glycyrrhiza glabra,Sophorae flavescentis and Phellodendri chinense Scheeid had no inhibition on the bacterium with MBC of more than 200 mg/mL.