The full-length of ORF5 gene was amplified from the genomic RNA of Henan variant PRRSV strain HN07-01 by RT-PCR.The amplified fragment was cloned into pMD19-T vector and then sequenced.Compared with the ORF5 gene sequences of BJ-4,classical American genotype VR-2332,HB-1 and JXA-1,the homology of HN07-01 ORF5 gene was 88%,89%,96% and 99%,respectively.The ORF5 gene was subcloned into the prokaryotic expression vector pGEX-6p-1,transformed into E.coli BL21 and induced with IPTG.The results of SDS-PAGE and Western-Blot confirmed that the recombinant protein of 41.5kD was successfully expressed in E.coli BL21.