Abstract: The morphology, biological characteristics, 18SrDNA and fungicide screening of the pathogen isolated from the root of tobacco from Feixian in Shandong province were studied. The results showed that pathogen of FBJ had pathogenicity of tobacco. Through morphological characteristics and 18S rDNA sequence analysis, FBJ was Sclerotium rolfsii Sacc. It could cause southern blight on tobacco. Biological characteristics displayed that the pathogen of FBJ grew well at the pH range of 5.0-10.0, with the optimal pH of 9.0. Hypha and sclerotia viability were completely lost when hyphal agar plugs and sclerotia incubated at 50℃ 10 minutes. Fungicide testing on PDA plates revealed that 70% Mancozeb showed the greatest inhibition of hyphal growth and sclerotia germination of S. rolfsii.