Abstract: This study has developed a three-dimensional CFD numerical method for simulation of the flows over a spillway dam using accurate river terrain. We used the CATIA design platform to construct a 3-D reservoir model for the Yujiahe project of Hubei, which combined the detailed geometry of buildings and structures with river terrain and captured the geometric details of spatial arrangement of a real hydraulic project. An RNG k-epsilon turbulence model and VOF method for tracking free surface were adopted. Flow velocity, water flow regime, and pressure on dam surface in the conditions of flow rates of 1669, 1199 and 728 m3/s were simulated. Comparison and analysis showed a good agreement of modeling results with the measurements of our scale model tests and verified the model. This study demonstrates the advantages of the new method in simulation of 3-D flows over complicated river terrain.