The Mesorhizobium huakuii 7653R （slow growing rhizobium） was revitalized to obtain strains AW-8 and AW-10 to study the synergistic effects of M. huakuii on planting Chinese milk vetch （Astragalus sinicus） in the field. The symbiotic nodulation and nitrogen-fixing capabilities of the strains obtained were verified with re-inoculation experiments. M. huakuii AW-8 was used as the core strain to compare the symbiotic phenotypes of four Mesorhizobium strains through a soil pot cultivation experiment. Results showed that the aboveground biomass， nodulation， and nitrogen-fixation indexes of M.huakuii AW-8-inoculated Chinese milk vetch were higher than those of the original strain AW7R-1， and AW-8， AB-21， and AZ-21 were identified as all elite strains. The aboveground biomass， nodule number， nodule weight， and the activity of nodule nitrogenase of the Xinzi No.1 variety of Chinese milk vetch inoculated with AW-8 increased by 41.3%， 87.8%， 34.2% and 6.3%， respectively. The results of comparing the inoculation effects of strain AW-8， AW7R-1， AB-21， and AZ-21 at urea nitrogen levels of 0 kg/667 m²， 3 kg/667 m²， and 6 kg/667 m² showed that the content of nitrogen and the accumulation of total nitrogen in the above ground hay of Chinese milk vetch increased by 9.5% and 4.1% when urea nitrogen level of 3 kg/667 m² was applied and AW-8 was inoculated， while the content of available phosphorus， available potassium， and organic matter in rhizosphere soil increased by 2.6%， 35.9%， and 0.5%， respectively. The results of comprehensive analyses showed that co-application of M. huakuii AW-8 inoculation and 3 kg/mu urea synergistically enhanced the accumulation of nitrogen and the total nitrogen in Chinese milk vetch plants， and improved nutrients in rhizosphere soil as well. It is indicated that the inoculation of M. huakuii AW-8 and the application of appropriate nitrogen fertilizer has a synergistic effect on planting Chinese milk vetch.