Abstract: In the hydraulic model test of Edie reservoir,it was found that the repelled downstream hydraulic jump occurred in the gradual expanding stilling basin,and the flow state was poor,which could not meet the requirements of energy dissipation and scouring prevention. In order to solve this problem,numerical analysis software FLOW-3D was used to explore the influence of the body type parameters of the gradual expanding stilling basin on the flow state,inundation degree,energy dissipation rate and so on in the stilling basin,The results show that:for the gradual expanding stilling basin with the repelled downstream hydraulic jump,increasing the height of the tail can significantly improve the inundation degree,the appropriate height of the tail sill can not only improve the flow state in the stilling basin,but also control the energy dissipation rate to a reasonable range;the increase of diffusion angle and pool length has little effect on the inundation degree and energy dissipation rate and is not beneficial to improving the flow state. Based on the results,a reasonable shape parameters was recommended and verified by physical model. The research results can provide a reference for design optimization in the same type of engineering.