Energy dissipation sills which is on the stepped spillway，is on the step surface，a small force pool is formed to increase the amount of air flow，to improve the flow pattern，increasing the elimination effect.The crisscrossed spillway reduces the cavitation damage to the steps，and which it can effectively slow down the erosion of the downstream channel and achieve the goal of elimination.This article through to the different size of stepped spillway numerically simulated，analysis of energy dissipation under different working conditions which including turbulence kinetic energy and turbulence dissipation rate，to get the optimal size and put forward some ideas for similar engineering.