To investigate the effect of soil O2 concentration on soil N2O emission and the abundance and composition of narG type denitrifying microbes in paddy soils, the quaternary red clay was incubated under three O2 concentrations of 0%(anaerobic), 10%, and 21%, and two soil water contents of 40% and 60%. The results showed that under both 40% and 60% soil moisture conditions, anaerobic treatment had the highest N2O emission flux, and the N2O emission flux under 60% soil moisture treatment was slightly higher than that under 40% soil moisture treatment. The analysis of variance indicated compared with soil water content, O2 was more important factor restricting N2O emissions in the soil. The abundance of narG gene of soil microbes was negatively correlated with O2 content(P<0.01), positively correlated with N2O emission flux and soil NO3–-N consumption mass fraction(P<0.01), and positively correlated with soil moisture content, but not significantly. Both O2 content and soil moisture content could cause the difference in composition of narG type denitrifying microbial community. In the 40% soil moisture treatment, OTU1882(Pseudolabs) and OTU1510(Mycobacterium) accounted for a larger proportion, while in the 60% soil moisture treatment, OTU1593(Geobacter) accounted for a larger proportion. When the soil moisture content was constant, the relative abundances of advantages OTU1882 and OTU1510 in anaerobic treatment at the same time were relatively low, and the variation amplitude were large, which were negatively correlated with N2O emission flux with a significant(P<0.05) effect for OTU1882. In summary, soil O2 content could regulate N2O emissions by regulating the abundance of narG gene and community composition of soil microbe.