Abstract: After the impoundment of the Three Gorges Reservoir, the increase of water depth caused the increase of the lag time of the sediment peak behind the flood peak in the flood propagation. The asynchronous movement characteristics between the flood and sediment peaks can be utilized to conduct the sediment peak regulation, one of the crucial measures to reduce the reservoir sedimentation. The three-dimensional numerical model named SCHISH (Semi-implicit Cross-scale Hydroscience Integrated System Model) was adopted to study the asynchronous movement characteristics of the flood and sediment peaks in the Three Gorges Reservoir. The reliability and accuracy of the model were verified by comparing the water and sediment transport during the flood season in 2013, then the asynchronous movement characteristics of the flood and sediment peaks under different impounded levels were preliminarily analyzed based on the model results. The results showed that the numerical model could accurately simulate the long-distance propagation of the flood and sediment peaks. The impounded level in front of the dam had little influence on the propagation time of the flood peak, but had a significant effect on the propagation time of the sediment peak. The increase of the impounded level resulted in the decrease of the flow velocity and the sand-carrying capacity, so the propagation speed of the sediment peak was slower and the sediment peak value was smaller, which led to the longer lag time of the sediment peak behind the flood peak along the reservoir. The research results can provide scientific evidence for further optimization of the operation of the sediment peak regulation in the Three Gorges Reservoir.