According to the sequence of ATCC VR-2332 strain of porcine reproductive and respiratory syndrome virus published by the Genbank, two pairs of primers were designed for RT-PCR amplification of PRRSV isolates from Liaoning. The corresponding DNA fragments were abtained and , cloned into pMD18-T vector respectively and sequenced in Shanghai. The sequences of ORF567 genes were analysed using DNAStar and compared with those of ATCC VR-2332,CH-1a, BJ-4 LV-M96262 and vaccine strains. Nuclear acid analysis indicates that the homology was up to 89.5%-95% between Liaoning strains and VR-2332,CH-la, B J-4, and 54%-58.3% between Liaoning strains and LV-M96262. Amino acid analysis indicates that the ho- mology was up to 82.8%-94.7% between Liaoning strains and VR-2332,CH-1a,BJ-4 .