The occurrence of soil-borne diseases is closely related to soil environment especially the bacterial communitystructure.Under the condition of natural diseases in thefield，the study on the change characteristics of soil environmental factors in the process of occurrence and development of soil borne diseases can more scientifically evaluate the relationshipbetween the occurrence of diseases and the change of soil environmental factors，and provide necessary scientific basis forfurther enriching the research on the occurrence mechanism of soil borne diseases.In three tobacco growing areas(ShilinBanqiao，Baoshan Qijie and Baoshan Zhujie)where tobacco black shank disease is more serious in Yunnan Province， a highly susceptible flue-cured tobacco variety，Honghuadajinyuan，was planted uniformly.According to the diseaseinvestigationcriteria，the infected tobacco plants were divided into different degrees(normal tobaccoplants，mildly infectedtobacco plants，moderately infected tobacco plants and severely infected tobacco plants).The rhizosphere soils of tobaccoplants with different disease severity werecollected，and the differences of soil enzyme activity and bacterial communityresults were analyzed and compared.The results showed that the activities of soil enzymes(soil urease，invertase，acidphosphatase，catalase)in rhizosphere showed decreasing trend with the severity of the disease increasing at different surveypoints.The high -throughput sequencing and diversity analysis of 16S rRNA in soil showed that the composition of dominantcommunities at the level of soil bacterial family wassimilar，and the relative abundance of actinomycetes decreased with theincrease ofincidence，while that of acidobacteriaincreased；The relative abundance of bacteria community in rhizospheresoil of different degree of disease was different，among which， Steroidobacteria，Adhaeribacter，Mesorhizobium and Tumebacillusdecreased first and then increased with the increase of diseasedegree；The α diversity index of bacterialcommunity was lower than that of healthy rhizosphere soil in differentdegrees，and the α diversity index of tobacco plantwith mild disease was the lowest，and the shannon and simpson index of tobacco plant with mild disease was significantlylower than that of healthy tobaccoplant；PCoA principal component analysis showed that the bacterial community structureof rhizosphere soil was significantly separated with the degree of disease，and along the second principal componentcoordinateaxis，the bacterial community structure was gradually increased with the degree ofdisease.To sumup，themain environmental factors in the rhizosphere of tobacco plants with different degrees of incidence are quitedifferent，thesoil enzyme activity is inhibited to differentdegrees，the composition of bacterial community changes intendency，thecommunity structure changes intendency，and the diversity of soil microorganisms decreases.