Abstract: The Three Gorges Project is a "national treasure". Fully leveraging the comprehensive benefits of the cascade reservoir system in the upper Changjiang River, with the Three Gorges Reservoir as its core, has long been a focus of attention from various sectors of society. In order to overcome the constraints imposed by sediment deposition on optimal reservoir operation under the premise of ensuring flood control safety and mitigating sedimentation risks, we focuse on optimizing the joint sediment discharge strategies for the cascade reservoirs in the upper Changjiang River. Based on new characteristics of sediment concentration during the flood season and the asynchronous propagation of flood peaks and sediment peaks, we investigate the mechanism of asynchronous flood-sediment peak propagation, establish a real-time sediment prediction model, and propose a refined sediment discharge strategy for the Three Gorges Reservoir under the joint operation of the cascade reservoirs. An integrated sediment discharge system encompassing "theory-simulation-operation" has been developed. The proposed strategy can increase the sediment discharge ratio by 4~9 percentage points, enabling refined operation that balances reservoir flood control and sediment management. The research outcomes not only provide theoretical and technical support for the joint optimal operation of cascade reservoirs, but also hold significant scientific values for advancing technical systems such as simulation of water and sediment generation and transport in large river basins, as well as reservoir sediment operation.