Under the background of "dual carbon",sewage treatment not only needs to achieve resource utilization,but also needs to reduce carbon emissions. N2O has been given special attention due to its warming trend far exceeding that of CO2 and CH4,and has also been rated as one of the greenhouse gases that pose the greatest threat to the ozone layer in the 21st century. Both nitrification and denitrification processes in sewage treatment produce N2O,and there are differences in the mechanism and method of producing N2O during the reaction process. The amount of N2O produced will also change due to different processes. Due to the high processing capacity of actual sewage plants and their strong resistance to fluctuations in water quality and quantity,as well as the extremely complex changes in water quality components and parameters,it is necessary to analyze the conditions that affect N2O production in urban sewage plants and further analyze the N2O emission mechanism.The results showed that the CANON process is the most efficient process of biochemical denitrification at present, and the N2O generation in the sewage plant was affected by the carbon source, dissolved oxygen concentration, temperature and carbon intensity of the magnetic field, and the temperature change caould not determine whether the enzyme activity or nitrification denitrification reaction equilibrium was changed, and the N2O emission of carbon source needed to be further studied in engineering practice.