Abstract: A leading obstacle to continuous cropping of potatoes is Rhizoctonia solani in the rhizosphere. An understanding of the relationship between potato soil-borne pathogen accumulation and continuous cropping was sought to overcome the obstacles to continuous cropping of soil borne diseases. Synergy Brands (SYBR) Green I Dye (SGI) real time fluorescent quantitative Polymerase Chain Reaction (Rt-PCR) was optimised to perform quick checks and quantification of R. solani in soils with potato damping off disease. The dynamic changes of R. solani in the rhizosphere soil of continuously cropped potato was investigated. Results show that, the methods can be directly applied to soil pathogens with quantitative detection of DNA, which can be detected to a minimum detection level of 1×10² copies/g in potato soil concentrations of R. solani. Amplification efficiency is high (1.04) with a low detection limit. The cumulative status of pathogenic bacteria in the rhizosphere soil can be readily assessed without isolation and culturing. With increasing years of continuous potato cropping, the numbers of R. solani in rhizosphere soil had an upward trend with the increasing year of potato’s continuous cropping, by the growth process, the numbers of rhizoctonia solani in rhizosphere soil were downward trend. The largest amount of pathogens accumulated is the pre-seeding period of five years, that is 3.75×10⁷ copies/g. This shows that continuous cropping led to a soil microbial population structure that increased the amount of change of soil pathogenic fungi. The infection probability of Rhizoctonia solani in early potato blight increased.