Abstract: Objective]The objective of this study is to develop a SYBR GreenⅠreal-time PCR for the detection of Peronospora farinosa f.sp.betea Byford rapidly.[Method]The real-time PCR primers were de-signed based on the reported 28S rDNA gene sequences of P.farinosa sp.betea Byford and similar species. Totally 6 pathogens of beet and other 5 pathogens and 12 samples of beet seeds were screened to test the speci-ficity and sensitivity and applicability in this assay.[Result]The SYBR GreenⅠreal-time PCR assay could detect positive amplification from P.farinosa f.sp.betea Byford only,negative results from other pathogens and negative control,and more than 100 fg genomic DNA of P.farinosa sp.betea Byford could be detected. The 12 samples of beet seeds from different sources were detected by this assay,suggesting that the results were consistent with the field monitoring results.[Conclusion]This assay can detect P.farinosa sp.betea By-ford rapidly,and offer a technology to early diagnosis and control P.farinosa sp.betea Byford.