To study its structure and function,the ORF81 gene was amplified by PCR from koi herpesvirus China’s Jilin strains(KHV-CJ)infected.Mirror carp primary fin cells were then cloned into the vector pMD18-T to construct the recombinant plasmid.The structure and function of the gene were studied by means of bioinformatics software,including phylogenetic tree analysis compared with other three KHV strains published in GenBank.The results showed that the length of the ORF81 gene,encoding 256 aa,was 771 bp.The molecular weight was 28 246.50 u and the isoelectric point was 8.404.The protein is hydrophobic.The most likely signal peptide cut was in 29 bit(Ser).ORF81 has four transmembrane regions.The antigenicity of ORF81 was good.According to the protein structure analysis,there may be no Nglycosylation sites,6 O-glycosylation sites and 11 phosphorylation sites.Phylogenetic analysis showed that he ORF81 gene of KHV-CJ was in the same branch with the Israel strain.Above all, ORF81 gene may have good immunogenicity.The study established the foundation for genetic background information,pathogenesis,molecular epidemiology and genetic engineering vaccine research of koi herpesvirus.