To study the water-sediment distribution and ecological environment changes in the Yellow River Estuary during the 2021 water and sediment regulation period， and to explore the impact mechanisms of water and sediment regulation on the hydrodynamics and ecological environment in the estuarine area， this paper is based on the Finite Volume Community Ocean Model （FVCOM）. A three-dimensional hydrodynamic and ecological model for the Bohai Sea was established， and remote sensing data were used to analyze the spatiotemporal variations of freshwater from the Yellow River， suspended sediment， nutrients， and chlorophyll-a concentration during the water and sediment regulation period. The results show that water and sediment regulation significantly altered the distribution and diffusion characteristics of freshwater and suspended sediment in the Yellow River Estuary. During the regulation period， the concentration of suspended sediment and nutrients in the estuarine area increased significantly， and the diffusion range of suspended sediment remained similar during both the sediment discharge and water discharge periods. However， due to the reduced river inflow， the diffusion range was somewhat limited during the sediment discharge period. Land-based substances were mainly concentrated on the southern and northern sides of the estuary， with the southern side having a wider diffusion range than the northern side. Meanwhile， during the water and sediment regulation period， the nitrogen-to-phosphorus ratio increased， and the input of nutrients promoted phytoplankton growth， leading to a significant increase in chlorophyll-a concentration. However， the increase in suspended sediment concentration caused light limitation， which partly offset the positive effect of increased nutrients on primary production. The study suggests that setting the sediment discharge period after the water diversion period is crucial for reducing light limitation and preventing harmful algal blooms. This research provides scientific guidance for optimizing the water and sediment regulation plan in the Yellow River Estuary， effectively controlling algal blooms， and maintaining the ecological environment.