Abstract: Since the completion of the Cao'e River sluice gate, problems related to scouring beneath the gate have been significant, with three rounds of anti-scour reinforcement measures implemented successively. To clarify the patterns of scouring and sedimentation beneath the gate and its main influencing factors, this study analyzed the impact of Qiantang River tidal bore, sluice gate discharge, and prior terrain on the scouring and sedimentation processes. This analysis was based on long-term empirical data, mathematical model results, and physical model experiment data. The research indicates that: (1) The tidal bore of the Qiantang River causes significant sediment deposition beneath the gate, with average monthly sedimentation reaching up to 2.2 m under no gate discharge conditions; (2) sluice gate discharge constitutes the primary dynamic factor responsible for deepening the riverbed beneath the gate by unilaterally transferring the sediment downstream. The relationship between gate discharge and the extent of scouring indicates that greater gate discharge results in a more significant decrease in the deepest elevation point beneath the gate; (3) the prior terrain beneath the gate also significantly impacts the extent of scouring and sedimentation. Under constant gate discharge, a higher initial terrain results in greater scouring. Through multiple regression analysis, a predictive model correlating sluice gate discharge and initial terrain with the extent of scouring beneath the gate was established, providing a reference for the operation and anti-scouring measures of the sluice gate.