Abstract: Our study built the shallow-lake mesocosm to simulate the N₂O exchange process at the water-air interface throughout the whole experimental periods under climate change and eutrophication. (1) Results of the mesocosm experiment demonstrated that constant and fluctuate warming significantly promoted N₂O emissions and annual accumulating emissions due to changes in metabolic processes and biotic interactions. Phosphorus addition affected the efficiency of denitrification metabolism in water to weaken the N₂O emission at the water-air interface and annual cumulative emission; (2) In the experimental periods, the dominant primary producer in the mesocosm changed from aquatic plant to phytoplankton, and the organic matter content in the water body accumulated continuously. Our study showed that the above two factors have a significant effect on the increase of N₂O emission from the water-air interface, and that the fluxes of N₂O from shallow lakes under climate change and eutrophication trends were mainly affected by changes in the ratios of N and P in water bodies and primary producers in the accumulation of organic matter. We concluded that constant and fluctuating climate warming can tilt the N₂O balance to higher emission, and the combination of warming and nutrients can cause complex interactions in the N₂O exchange in the water-air interface.