A robust and accurate 3D CIP-based model is developed, capable of capturing correctly complex three-dimensional free surface flows and, even more important, also capable of predicting an accurate pressure force.The flow is represented by one set of governing equations, which are solved numerically on a non-uniform, staggered Cartesian grid by a high-order finite difference method.The governing equations are divided into an advection step and two non-advection steps by making use of a time splitting method.A CIP method is adopted to calculate the hyperbolic equation for velocity at the advection step.The free surface is immersed in the computation domain and expressed by a one-fluid density function.With this treatment the dynamic conditions at the free surface are automatically satisfied.The validity and utility of the numerical model are demonstrated by applying it to a 3-D dam-breaking problem and compared with a performed experiment.Three free surface capturing methods-VOF, CIP and THINC-are used for the interface capturing.Main attention is paid to the free surface and impact pressure.Numerical results show that the present CFD model is both robust and accurate for violent impact free-surface flow.