Abstract: In order to solve the engineering problems of secondary hydraulic jump and downstream river bed erosion due to insufficient energy dissipation in deep tailwater stilling basin, this paper compares the stilling basin flow fields of flat gate pier, conventional flaring gate pier and incomplete flaring gate pier based on the physical and numerical models. Results show that through increasing velocity gradient and lateral water level gap between adjacent chambers, the incomplete flaring gate pier can promote the lateral diffusion and collision of water jets to form growing vertical vortex from bottom to surface in the upper regions of stilling basin. This would significantly intensify energy dissipation to reduce the outgoing velocity, and completely solve the common hydraulic problems in deep tailwater stilling basin.