Abstract: Filter-feeding fish play an important role in coping with the eutrophication process of water bodies. In order to understand the effect of filter-feeding fish faeces on N₂O emissions from lake sediments, we collected sediments, water, and feces of Hypophthalmichthys molitrix in Qiandao Lake, and set up three experimental groups according to different ratios. A 90-day simulated closed culture transformation experiment was carried out. The key microbial strains affecting nitrogen transformation and the main environmental factors influencing nitrogen transformation were identified by analysing the emission flux characteristics of N₂O, the physicochemical indexes of water and sediment mixtures, nitrogen metabolism enzyme activities, and microbial sequences. The results showed that under the influence of fish faeces, the N₂O emission flux at the water-gas interface reached the highest on day 45 and then decreased rapidly. From day 45 to day 60, the flux shifted from emission to uptake. The greater the proportion of fish faeces added to the sediment, the greater the uptake of N₂O during the later stages of incubation. The addition of fish faeces significantly increased the concentration of soluble carbon and ammoniacal nitrogen in the recirculation system, while decreasing DO in the water column. . It also significantly enhanced the activities of four relevant nitrogen-converting enzymes in the sediments. 16sRNA analysis of the sediments showed that the addition of fish manure significantly increased the relative abundance of Proteobacteria, Firmicutes, and Bacteroidota. The increased abundance of Bacillus probably being the main reason for the sediments to show stronger N₂O uptake efficiency. This provides a theoretical reference for the N₂O abatement mechanism of filter-feeding fish proliferation in lakes.