Using the VOF method to simulate free surface and unstructured grid to deal with complex boundary shape, and conducting the appropriate district based on the border form and utilizing the two phase flow of k-ε water-gas simulating the flow field of the stepped spillway and smooth spillway, the flow field, water surface profile and energy dissipation rate, and other related hydraulic parameters are gotten. The numerical simulation results show that the water flow on the stepped overflow dam face is turbulent with full aeration, the rate of energy dissipation on the steps with choosing a reasonable size is higher, and the physical model test results are analyzed. By comparison, the simulated results are in good agreement with test data, so the two-phase turbulent flow model and the VOF method used for flow simulation on stepped dam face is feasible.