Abstract133 phenotypic features (nutrition utilization , antibiotic resistance ,tolerance to NaCl and alkali , enzyme activity)of 48 strains isolated from Medicago sp. , Melilotus sp. , Caragana sp. , growing in arid regions , were analyzed. The result shows that there are great diversities among strains isolated from the the same hosts growing in different geographic origin. Through the numerical taxonomy , 41 unknown strains are clustered into three new groups , at the similarity level of 85 %. The main host plant of strains in group 1 is Medicago , the main host plant of strains in group 2 is Melilotus , the host plant of strains in group 3 is Caragana. XJ96 333 (the host plant is Melilotus) was clustered with group 1 at the similarity level of 84 %. NM 020 (the host plant is Caragana) was clustered into R. leguminosarum at the similarity level of 88 %. NM 183 and NM 218 (the host plant is Caragana) were clustered into S . fredii at the similarity level of 86 %. XJ96 482 (the host plant is Medicago sativa) was clustered with other examined strains at the similarity of 67 %. Strains in group 1 ,2 and 3 can grow on YMA with 2. 0 % (340 mM) NaCl ,pH 9. 0 and in 40 ℃. Strains in group 3 can also grow on YMA with 3. 0 % (510 mM) NaCl. 90 % of strains in group 1 and all strains in group 2 ,3 can grow at 10 ℃,which shows that all examined strains of group 1 ,2 ,3 are resistant to NaCl and alkali ,low temperature and high temperature. Group 1 and Group 2 shared a similarity of lower than 85 % with S . melioti . This shows phenotypic feature diversity of strains in the group 1 and group 2