The role of ABC transporter permease gene atpA in the symbiotic nitrogen fixation between Rhizobium and legumes in Mesorhizobium huakuii 7653R was studied. The atpA mutant strain HKatpA was constructed through homologous recombination. The functions of the mutant stain in the growth and symbiosis of Astragalus sinicus L. was studied. The results showed that the mutation in the atpA gene caused rhizobia to early enter a stable period and weaken its ability to form biofilm. The plants inoculated with the mutant strain had yellow leaves， and prominent symptoms of nitrogen deficiency， with their plant height， fresh weight of the above-ground parts， number of nodules， and the activity of nitrogen fixing enzyme decreased by 14.3%， 33.3%， 31.5%， and 18.8%， respectively. 78 differentially expressed proteins were identified with proteomics analysis. Compared with wild-type bacteroids， 23 proteins in atpA gene mutant bacteroids were up-regulated and 55 proteins were down-regulated. Among the differentially expressed proteins， 10 proteins were related to amino acid transport， and 12 proteins were related to nitrogen-fixing complex formation in nodules. It is indicated that the ABC transporter permease gene atpA in Mesorhizobium huakuii plays an important role in the process of growth and symbiosis with the host plant Astragalus sinicus L..