Abstract: A realizable k-ε two-equation model for turbulent flow and a VOF method were adopted in the present study to simulate the flows in a vortex shaft spillway that has super-high working heads and large flow capacity, and the simulated flow pattern, cavity radius, pressure distribution, free water surface profile, rotational angle and other characteristics of the flows were examined. The results indicate that rotating flows in this vortex shaft have an uneven distribution in thickness of the water layer on the shaft wall, with greater thickness in the mainstream area. The gradient of stream-wise attenuation in tangential velocity of the rotating flows is gradually reduced from top to bottom. In the upper part of the shaft, axial velocity increases rapidly with the decreasing potential energy. When the flow reaches the middle and lower part, its axial velocity keeps increasing rapidly in the mainstream area, but the increase is significantly slowed down in the other area. Comparison of the numerical simulations with the measurements on a scale model shows a satisfactory agreement and the reliability of the method adopted.