Using bioinformatics analysis, a rich antigenic determinant area in HEP-Flury nucleoprotein sequence was selected, and the codons were modified to cater the codon usage bias in Escherichia coli, and the restriction enzyme sequences were inserted in upstream and downstream. The modified gene was synthesized and cloned into prokaryotic expression vector pET-32a(+). The recombinant plasimd was designated pET-32-NP. pET-32-NP was175 transformed to E.coli BL21(DE3)pLysS, and the recombinant protein was expressed after IPTG induction. SDS-PAGE analysis showed that the expressed protein had a relative molecular mass of 34 000. Western-blotting results also revealed that the expressed protein could be recognized specifically by mouse anti-His monoclonal antibody and mouse anti-RV polyclonal antibody.