Abstract: For the dam site of Wudongde Hydropower Station, the valley is narrow and the covering layer is deep. During the design stage of the detailed construction, the arch dam thickness was increased, and the relative position of the surface and middle hole changed. Therefore, there are some problems, for example, the overflow water from surface outlet hits the middle outlet arc gate, the flow from surface, middle and bottom outlets collides with each other, which cause lateral splash water and then strikes the permeable slope, and strong erosion happens on the water cushion pond. Through the 1:50 hydraulic integral model test, the surface outlet position and the type were optimized. After the shape optimization, the flow from surface outlet diffused laterally with clear longitudinal stratification, thus the erosion became slight after energy dissipation, and the lateral splash water intensity on the slope was basically as strong as natural precipitation. The test results can provide technical support for engineering design and safe operation.