Abstract: During the impoundment period of the Three Gorges Reservoir, when the deep-holes of flood discharge is operated under the high water level, problems often generate such as a vertical vortex in front of the dam and unstable flow pattern in the chute.Therefore, to improve the flow pattern in front of the dam and improve the safety of flood discharge facilities, a large-scale model test of flow turbulence characteristics of deep-hole chute, numerical simulation analysis of flow field and vortex in front of the dam, and optimization model test of flood discharge scheduling were carried out.The results showed that the vertical vortex in front of the dam was formed by the combined action of upstream oblique inflow and deep hole flood discharge, and the vortex in front of the dam was a surface vortex.The oblique inflow of water flow would increase the swing of the aeration cavity and the turbulence intensity of the water flow in the deep-hole chute, causing the intermittent uplift of the water body.When using deep-hole discharge under high water levels, the positive inflow condition in front of the dam should be maintained.Using surface-hole facilities could improve the flow field in front of the dam and eliminate the vortex.During the impoundment period of the Three Gorges Reservoir(water level above 170 m),it is feasible to open the surface hole first and then open the deep hole for flood discharge.