Although slip-type flip bucket is widely used in hydraulic projects, there is no mature method to design it. The bucket type is designed preliminarily according to similar projects, and is optimized through model test. However, model test features with long time, high cost,and low accuracy of conventional instruments. In this article, three-dimensional numerical simulation is carried out on the slip-type flip bucket at the flood discharging tunnel of Xiaowan hydropower station in association with RNG k-ε turbulence model and FAVOR technology of Flow 3D. The computation results of some main hydraulic parameters inclusive of water depth, water jet shape, point of jet entering water in the downstream and upstream, peak height of water jet, and angle of water jet are in accordance with model test and prototype observation. Flow 3D could save time and cost in designing slip-type flip bucket.