Reservoir dredging is of great significance in solving the sedimentation problem and maintaining reservoir functions. Taking Fengjiashan Reservoir as the research object, this paper elucidated the necessity of reservoir dredging, and proposed three dredging schemes with the aim of expanding the reservoir’s effective storage capacity. Based on numerical simulations, the results indicate that dredging has little impact on the sedimentation volume in the reservoir. Dredging can increase the water depth and reduce the flow velocity in the reach upstream of the reservoir, which is conducive to the sediment deposition within the dredging area, thus reducing the sediment deposition in the main channel in front of the dam. It was found that dredging closer to the first widened reach in the reservoir resulted in more noticeable backfill effects.