Over the past decade, due to the addition of new genera and species to this important bacterial group, the classification of rhizobia has been gone through a substantial change. The recent progress of the classification of the rhizobia from the second edition of Bergey’s Manual of Systematic Bacteriology to date was summarized in the paper. Browse our selection of published papers have shown a great diversity among nitrogen-fixing bacteria isolated from different legumes. Currently, about 100 species belonging to 17 genera of α-, β- and γ-Proteobacteria have been described as rhizobia. Class of α-Proteobacteria include the genera Rhizobium, Sinorhizobium, Ensifer, Shinella, Neorhizobium, Pararhizobium, Mesorhizobium, Bradyrhizobium, Phyllobacterium, Methylobacterium, Microvirga, Ocrhobactrum, Azorhizobium and Devosia; Class of β-Proteobacteria include Burkholderia and Cupriavidus (formerly Ralstonia); Class of γ-Proteobacteria include Pseudomonas. There are about 748 genera and 19 700 species of leguminosae plants around the world, and about 172 genera and1 485 species of leguminosae plants in China. Among of the 19 700 species of leguminosae plants, only 23% leguminous plants have been surveyed the ablilty of nodulation. Therefore, it is necessary to survey the different regions of legumes using advanced methods, and we can obtain the new rhizobia resources.