The paper is about the systematic studies of biological characteristics of 15 stains rhizobia isolated purified from Acacia confusa grew in Guangxi karst environment. The results showed that there were typical characteristics of rhizobia .there were negative reaction about use of 3-ketolactose and beef extract peptone nutrient agar medium ,and positive reaction about use of starch and citrate medium ,and produce acid in reaction of BTB and litmus milk medium, (NH4 )2HPO4 was used as nitrogen sources and both four monosaccharides and three disaccharides could be utilized as carbon sources in 15 strains rhizobia isolated Acacia confuse .Among the 15 strains for the tests, 11 strains could deoxidize the nitrate of medium into nitrite, 14 strains could grow well on NaCl solution concentration 3.0 % ~ 4.0 % , 14 strains could grow at 39℃, 13 strains may grow on highest pH12 and 4 strains on lowest pH4 cultrue medium. 15 strains can grow in 10% and 11 strains in 10%~30% of CaCO3 solution concentration.