Abstract: 【Objective】 To study arbuscular mycorrhizal fungi（AMF）infection symptom difference in roots and rhizosphere soil of Yunyan 121 in healthy and black shank infected tobacco plants，so as to provide theoretical reference application of AMF in soil-borne disease alleviation for tobacco plants.【Method】 Roots and rhizosphere soil of healthy and black shank infected tobacco Yunyan 121 were taken as experimental materials，microscopic morphology observation method was taken to determine AMF infection level and AMF spore density in rhizosphere soil.AMF diversity and community structure of tobacco roots were analyzed by using Illumina high-throughput sequencing technology.Redundancy analysis （RDA）and spearman correlation coefficient was conducted to reveal effects of physiochemical properties of rhizosphere soil on AMF diversity and relative abundance at genus level.【Result】AMF was detected in the roots and rhizosphere soil of healthy and black-shank-infected Yunyan 121 plants.Rhizosphere soil spore density and the AMF infection rate of healthy tobacco were significantly higher than those of infected tobacco plant.High-throughput sequencing detected 1410 AMF-OTUs in tobacco roots，belonging to 1 class，4 orders，5 families and 6 genera.Roots of healthy and infected tobacco had different dominant orders，families and genera of AMF seem from different taxonomic levels.Compared with diseased tobacco plants，healthy tobacco plant had higher ACE，Shannon and Chao indexes of AMF and lower Simpson indexes of AMF in roots，with difference reaching a significant level（P<0.05）.Principal component analysis showed that infection of black shank disease could dramatically change the AMF community structure of Yunyan 121 roots.RDA showed that soil available nutrients were negatively correlated with Chao，ACE and Shannon indexes of AMF，and positively correlated with Simpson index.Available phosphorus and available potassium were the main influencing factors for AMF diversity，and available phosphorus had the greatest influence on the relative abundance of AMF in tobacco roots at genus level.【Conclusion】Compared with healthy tobacco plants，available nutrient content in rhizosphere soil of infected tobacco plants increases and AMF spores density in soil decreases；and in tobacco roots，AMF infection rate decreases，the AMF species and diversity decreases，and AMF community structure changes significantly.