<p>Bacteria play important roles in the biogeochemical cycling of reservoir sediments. Whether there are differences in the community assembly processes of abundant and rare bacteria in reservoir sediments remains unclear. The distribution and assembly processes of abundant and rare bacteria from the sediments of Yutan Reservoir were revealed based on 16S rRNA gene amplicon sequencing. The results indicate that bacterial communities were sensitive to spatial and environmental variation. Proteobacteria, Acidobacteriota, and Chloroflexi were the top three dominant phyla of both abundant and rare bacteria, while their relative abundance ranking differed. Significantly higher values of node-level topological features and niche breadth were found in abundant bacteria, suggesting that abundant bacteria play important roles in maintaining the structure stability of the co-occurrence networks than rare bacteria. The abundant bacterial communities were mainly driven by stochastic processes (dispersal limitation), while the deterministic processes (heterogeneous selection) dominated in the rare taxa. Co, As, and electrical conductivity were identified as the most important factors affecting bacterial community structure. This study illustrated the distinct distribution and assembly processes of abundant and rare bacteria in reservoir sediments, enhancing our understanding of bacterial ecological processes in reservoir ecosystems.</p>