Ferric iron [Fe(Ⅲ)] reduction coupled with anaerobic ammonium oxidation (Feammox), a novel nitrogen removal pathway discovered in recent years, may play an important role in nitrogen self-purification in aquatic ecosystems. However, current research on this process is mainly focused on wastewater treatment or agricultural soils, with limited studies in natural lakes. In this study, sediments collected from different areas of Lake Taihu were anaerobically cultured and the bacteria involved in the iron and nitrogen cycles, the factors influencing Feammox and the potential rates in the sediments were investigated using high-throughput sequencing and isotope technology. During anaerobic culture, changes in the concentrations of iron [Fe(Ⅱ)] and various forms of nitrogen, as well as the morphology and colour of the sediments, indicated the presence of Feammox in the sediments, with nitrate (NO^-₃) being an important product of ammonia (NH⁺₄) oxidation. The addition of NH⁺₄ can promote the reduction of Fe(Ⅲ), but excessive NH⁺₄ can have an inhibitory effect. In the treatments with different Fe(Ⅲ) additions, there were no significant changes in NH⁺₄-N (P>0.05, ANOVA). However, the NO^-₃-N concentration in the treatment with the highest Fe(Ⅲ) addition was significantly higher than in the other treatments (P<0.01, ANOVA), indicating that Fe(Ⅲ) addition could promote the production of NO^-₃-N. The concentration of NO^-₃-N increased sharply and then decreased rapidly during anaerobic culture, accompanied by a significant increase in the relative abundance of genera associated with denitrification, indicating that the coupling of Feammox and denitrification occurred in the system. The results of the isotope enrichment experiment showed that the potential rates of Feammox were relatively high in different regions of Lake Taihu (0.17-0.51 mg N/(kg·d)), indicating that Feammox may play an important role in the nitrogen self-purification of Lake Taihu.