Abstract: In order to establish a RT-PCR method which was able to discriminate the classic strains, highly pathogenic strains and vaccine strain TJM-F92 of porcine reproductive and respiratory syndrome virus （PRRSV）, two sets of primers （1st and 2nd） were designed based on the published nucleotide sequences of Nsp2 gene of PRRSV in GenBank. The size of expected amplified fragments of LP-PRRSV, HP-PRRSV and HP-PRRSV TJM-F92 in RT-PCR assay using the 1st primers were 587,497 and 497 bp, respectively. The size of expected amplified fragments of HP-PRRSV and HP-PRRSV TJM-F92 in RT-PCR assay using the 2nd primers were 1004 and 644 bp, respectively.The discriminative diagnosis could be made according to the results of the two RT-PCR assays. Furthermore, the specificity, sensitivity and repeatability of the method were evaluated. The results showed that the established RT-PCR method had good specificity, sensitivity and repeatability and could be used to identify the classic strains, highly pathogenic strains and vaccine strain TJM-F92 of PRRSV.