Abstract: Along with the continuous cropping of tobacco, diseases and pests were aggravated, and tobacco yield and quality declined. In order to explore the fluctuation of tobacco soil physical and chemical properties and microbial flora under the continuous cropping conditions. Here, we picked the 5 different continuous cropping years(0,1,2,3,4) tobacco yields as 5 treatments (T0,T1,T2,T3,T4) respectively and the soil samples were sampled at the period of rosette stage, the vigorous growth and mature period respectively and we then tested the soil nutrient content and microflora changes. The results indicated that with the increasing of continuous cropping years, the available potassium content was significantly decreased accompanied with the promotion of available phosphorus content and the quantity of soil fungi. Bacteria and Actinomycetes, however, decreased. This showed that continuous cropping could change tobacco-growing soils physical and chemical properties, and transform the fungi type to the bacterium type. Both may be the cause of continuous cropping obstacles.