A one-step real-time Taqman RT-PCR assay for porcine reproductive and respiratory syndrome virus(PRRSV) was developed to detect the two type of PRRSV,American and European strain,by targeting the ORF7 gene of the virus.This new assay was compared to commercial methods developed by applied biosystems company.Quantitation was performed against a standard samples of the PRRSV for which a minimum of 10 copies per reaction were detected with a corresponding Ct value of 0.74%-1.52% and it shows no cross reaction with other swine pathogens.By detecting 40 clinical samples of the virus,the results are the same as the commercial kits.