Edwardsiella was first described as a distinct genus within Enterobacteriaceae, including E.tarda, E.ictaluri and E.hoshinae.E.tarda is the most predominant species as it is a common inhabitant of broad environment niches including fish, humans, reptiles, amphibians, chickens and other warm-blooded animals.The aim of this study was to classify Edwardsiella strains isolated from China aquaculture based on biochemical and molecular methods.In this study, biochemical characterization of 19 E.tarda isolates and two E.ictaluri isolates were performed with API 20E system.Other pathogenicity related phenotypes such as hemagglutination, haemolytic activities, and lethality to fish were also examined in these strains.Since it was difficult to categorize the subgroups ofE.tarda according to their origins or phenotypic properties, three PCR-based methods, i.e.PCR amplification of virulence genes,ERIC-PCR, and BOX-PCR, were carried out to further resolve the relatedness of the E.tarda isolates.As a result, all E.tarda isolates could be generally grouped into pathogenic and nonpathogenic branches before being classified into strain specific or origin specific clades.Biochemical characterization was sensitive for interspecific typing, while PCR based approaches permitted a more accurate discrimination for intraspecific typing resulting in pathogenic and nonpathogenic clusters and further more delicate clades for Edwardsiella.PCR-based genomic fingerprinting to study the relatedness and trace the pathogenicity of the Edwardsiella strains will be helpful in investigating virulence factors of Edwardsiella and in development of vaccines and diagnostics for edwardsiellosis.