Five treatments including no nitrogen application （CK），conventional nitrogen application （MRN） and reduced nitrogen application by 20%，40% and 60% （MRN1，MRN2 and MRN3） under the condition of mixed sowing of Chinese milk vetch and rapeseed were used to study the effects of mixed sowing of green manure and combined application of nitrogen fertilizer on the rice yield，the carbon and nitrogen and microbial community in soil，and the main environmental factors affecting microbial community structure.The rice yield and its components，the carbon composition，the nitrogen composition and relative abundance of microbial community in soil were measured.The effects of carbon and nitrogen on microbial community were analyzed.Results showed that the yield of early rice and late rice increased by 24.42%-39.23% and 19.34%-31.59% compared with CK treatment.The effect of MRN1 treatment on early rice and late rice was the best.Compared with CK，the content of nitrate nitrogen，ammonium nitrogen and alkali-hydrolyzable nitrogen in MRN1 was significantly（P<0.05） increased by 22.07%，19.05% and 11.20%，respectively.The content of soluble organic carbon and easily oxidized organic carbon in soil increased with the decrease of nitrogen application.The content of nitrate nitrogen and alkali-hydrolyzable nitrogen in soil decreased with the decrease of nitrogen application rate.The dominant bacteria were Chloroflexi，Proteobacteria，Acidobacteriota，Actinobacteriota，Firmicutes.Applying nitrogen fertilizer increased the evenness index of bacterial community.The content of alkali-hydrolyzable nitrogen，nitrate nitrogen and ammonium nitrogen was negatively correlated with dominant flora.The content of microbial nitrogen，easily oxidizable organic carbon and soluble organic carbon was positively correlated with dominant flora.The environmental factors having the greatest influence on the bacterial community structure were alkali-hydrolyzable nitrogen，microbial biomass nitrogen and soluble organic carbon.It is indicated that the mixed sowing of green manure and nitrogen reduction by 20% increase the rice yield and the content of inorganic nitrogen in soil，the community abundance of dominant bacteria，which is conducive to the reduction of emissions and the increase of efficiency in paddy fields，and the maintenance of the stability of ecosystem in paddy field.