In order to study the coupling relationship between methane oxidation and denitrification under different oxygen concentrations, three leaching bed bioreactors were used to simulate the microaerobic and anoxic environment in a semi-aerobic landfill. The coupling effect of methane oxidation and denitrification was discussed,and the related microbial communities were analyzed. The results showed that the maximum denitrification efficiencies of the microaerobic system and anoxic system were 100% and 85.67%, respectively. The maximum denitrification rates were 16.54 mmol/(L·d) and 9.88 mmol/(L·d), respectively. Denitrification process did not occur in the control system without methane. Therewas a good correlation between methane oxidation and denitrification in both microaerobic and anoxic systems. Introducing 30%~40% CO2 into the above two systems will stabilized their pH at 7.6 and 7.4, respectively, and had a good buffer effect on the accumulation of denitrification alkalinity. The dominantbacteria for methane oxidation were Methylobacter and Methylomonas, and the coupled denitrifying bacteria were mainly Methylobacillus.