Based the method of numerical simulation, this paper simulated and calculated the discharge capacity of original design scheme of stepped spillway, the line of water surface and the equal value line of pressure when sluice gate was fully opened, as well as the velocity distribution along the element process field by use of FLUENT software. According to the simulation result, it analyzed the deficiencies and problems existing in the original design scheme, and put forward a new scheme of optimization design. The simulation results have indicated that the new scheme can meet the practical requirement of engineering design, and can provide a valuable reference for optimization design of the same type of stepped spillway.