Total of 44 isolates were isolated from nodules of soybean grown on ferralsols of CuJut district (24 isolates) and Buonho town (20 isolates). The microsymbionts causing nodules on the roots of soybean (Glycine max L. Merr.) and 34/44 rhizobial isolates were analysed with 16S-23S intergenic spacer and PCR-RFLP for repeated sequence RSα a 1195-bp DNA fragment, indole acetic acid production and nitrogen fixing activity. Almost isolates produced IAA but they had the different nitrogen fixation capacity. All the strains were fast-growing soybean rhizobia (Sinorhizobium [Ensifer) fredii except two isolates (CJ02 and CJ09) were slow-growing soybean rhizobia (they were identified with sequence RSα as molecular marker for Bradyrhizobium japonicum). The study also showed the low presence of soybean nodulating slow growers in ferralsols of western highland of Vietnam.