Abstract:The Rhizobium sp. strains 8638L, 8638M and 86385 were isolated from root nodules of Albizia falcataria which were Gram-negative rods with a subpolar flagellum, the cell sizes being 0.53 ×1 .17, 0.66 ×1.95 and 0.66 × 2.03 up, respectively. The growth of the three strains colonies in yeast-mannitol (YM) liquid medium had long doubling time (7.79, 10.16 and 8.7 h, respectively). They grew slowly on YM agar, and could produce alkali, but could not grow on medium with 5% NaCl and at 39 ℃. Physiological and biochedrical characteristics of the three rhizobial strains were examined. The nodulation and nitrogenase activity in seedlings of A. falcataria inoculated with the strains isolated from nodules of the same tree species were tested, which provided satisfactory results. The strains were shown to have nitrogen fixing ability under self-growing condition.