Abstract: In order to evaluate of nitrogen biological fixation ability by different strains of Rhizobium legominosarum biovar phaseoli in common bean Iranian cultivars, a spilt plot experiment in randomized complete block design was conducted a field in Shahrekord, Iran. The factors were four bacterial strains: L-78, L-47, L-125, l-109, non-inoculated controls including application of nitrogen fertilizer treatment (100 kg N ha-1), without application of nitrogen fertilizer and three cultivars: local cranberry bean, Talash cranberry bean and local red type. The results showed that seed inoculation with strain increased nodule dry weight, N total (shoot) and percentage of fixed N2 in relation to bean rhizobia population naturalized and +N control. However, an efficient symbiotic was achieved with strain L-109, since total N content of plants inoculated with these strains was similar to that of plants supplied with N-fertilizer treatment.