The cpsE gene of Streptococcus agalactiaevirulent strain isolated from tilapia was amplified by PCR with specific primers and cloned into pMD19-T vector.The recombinant plasmid was strongly confirmed by PCR combined with restriction enzyme digestion(BamHⅠ and Hind Ⅲ).Molecular characterization analysis of cpsE gene was performed by bioinformatics tools like Clustal X 2.0,MEGA 4.1, Bioedit 7.0,TMHMM,NetPhos 2.0,NetNGlyc 1.0,SignalP 3.0 Server,PSIpred,SAM_T08 and CUSP.Results indicated that amino acid sequence deduced by cpsE of tilapia S.agalactiae was highly conserved and has revealed a surprising degree(100%)of homology among strains isolated from human and other mammals.Polypeptide analyzed in this study contained a Glycosyltransferases superfamily conserved domain that functioned as enzyme that catalyzed the transfer of sugar moieties from activated donor molecules to specific acceptor molecules.Moreover,the polypeptide possessed 3 phosphorylation sites which related to posttranslational modification.The hydrophilic regions were larger than hydrophobic regions and transmembrane domain was predicted to exist in polypeptide chain.The analysis of codon bias demonstrated the codon usage frequency of cpsE of tilapia S.agalactiaewas distinctly different and it preferred to perform in eucaryote.