Abstract: Rhizobial strains were isolated from soils growing with soybean cultivar Heilong 33 and Willimas.Fifty Sinorhizobium fredii strains were chosen,and their biological characteristics including growth velocity,acid-alkali endurance,resistance of intrinsic antibiotics,utilization of carbon and nitrogen sources,absorption of congo red,ability of melanin production,and plasmid profiles were comparatively researched.The dendrogram was described using the method of cluster analysis,and the biodiversity of Sinorhizobium fredii from different soils was proved.