Matrix protein is one of the structure proteins of infectious haematopoietic necrosis virus(IHNV),and its synthesis leads to apoptosis or programmed cell death in the transfected cells.To study its structure and function,the open reading frame of matrix protein gene was amplified by RT-PCR from IHNV-Sn isolate and cloned into plasmid pET27b(+)vector.The structure and characteristics of the gene were studied by means of bioinformatics software.The results are described as follows:the length of the M gene,encoding 195 aa,was 588 bp.The molecular weight was 21.88 ku and the isoelectric point was 9.35.The matrix protein was rich in serine,threonine and alkaline amino acid,and was composed of plenty of α-helix,extended β and coil.The protein is hydrophobic with no signal peptide and transmembrane regions.The antigenicity of matrix protein was good.According to the protein structure prediction,there might be no N-glycosylation sites,and there were 7 O-glycosylation sites and 15 phosphorylation sites in matrix protein.Phylogenetic analysis showed that the IHNV-Sn isolate was in the same branch with the isolates from America.The study established the foundation for genetic background information,pathogenesis,molecular epidemiology research of IHNV.