The hydraulic characteristics of smooth spillway, stepped spillway and pre-aerator stepped spillway were studied. The experimental investigations showed that the pre-aerator equipment can not only keep the stepped spillway’s large energy dissipation ratio but also protect the step’s surface from cavitation erosion by controlling the aeration concentration in stepped spillway. Model test results indicated that the energy dissipation ratio of the pre-aerator stepped spillway can reach to 70% at various discharge. The measured value of the aeration concentration was bigger than 5% at the vertical surface of steps. The -aerator stepped spillway had a better characteristic of against cavitation erosion and its energy dissipation ratio was higher than that of the smooth spillway. The pre aerator stepped spillway can be applied to the practical engineering with high water head and large unit discharge(exceed to 50 m^3/s).
