Abstract: The research aimed on the effect of matching between varieties of Astragalus sinicus and strains of Rhizobium on forming root nodule of milk vetch.The results showed that:rhizobium M10 enhanced nitrogenase activity significantly in variety 8410441, Minzi 6and Yijiang, increased the number of root nodules and their fresh weight.Rhizobium ZLH2 increased fresh weight of plants for variety 8410441 remarkably and rhizobium ZK7 increased total nitrogen content of variety Minzi 1.The strains M10, XZ, ZLH2, ZK7 and M3exhibited improving effect in nitrogen fixation for varieties Minzi 6, 8324411, 8410441, Yujiang Daye, and Yijiang, respectively, especially in the best effect of ZLH2.The nitrogenase activity of the azotobacter was negative correlation with the number of root nodules but increaseing nodule weight significantly, while total fixation amount of nitrogen was correlative positively with milk vetch yield and nitrogen content.Over all, strain ZLH2 was optimal in enhancing the growth of Minzi 6and 8410441, strain M10 was good to 8324411 and Yijiang, and strain ZK7 was to Yujiang Daye.