Since the operation of the Three Gorges Reservoir, the tributaries have burst out different degrees of bloom, especially the phosphorus eutrophication in Xiangxi River Bay, which has a great impact on the overall water environment and water ecological security of the Three Gorges Reservoir area. Sediment is an important internal source of phosphorus eutrophication in lake and reservoir water, and microbial community plays an important role in the element cycle of sediments, and microbial activity in sediments can significantly affect the morphological changes of phosphorus in sediments. In order to explore the diversity characteristics of microbial community structure in the sediments of Xiangxi River, a tributary of Three Gorges Reservoir, and its response to environmental factors, samples were collected at five representative sites in Xiangxi River during the four seasons from autumn 2021 to summer 2022, based on 16SrRNA high-throughput sequencing analysis and water quality analysis. The bacterial diversity and community structure differences were studied. The results showed that the abundance of microbial diversity was high in the sediments of Xiangxi River. The α diversity index showed a seasonal variation pattern of autumn > winter > spring > summer. The β diversity showed that the microbial communities in the bay had the greatest difference in spring and the least difference in winter. The dominant bacteria are Proteobacteria, Bacteroidota, Acidobacteriota, Nitrospirota, Desulfobacterota, Firmicutes, Chloroflexi, Verrucomicrobiota, Actinobacteriota and so on; Spearman correlation analysis and RDA redundancy analysis showed that overlying water pH value, dissolved oxygen (DO), electrical conductivity (Spcond), overlying water orthophosphate（PO43-）, water temperature (T) and total phosphorus (STP) in overlying water were the main environmental factors affecting the structure and distribution of bacterial community, and STP was the most critical factor. This study is helpful to further understand the effects of microbial seasonal changes on the phosphorus form and content in the sediments of the reservoir bay of Xiangxi River, and provide reference for the improvement and management of water environment in the Three Gorges Reservoir area.