Abstract: A new efficient characteristic-based numerical model for 3-D shallow water is presented and discussed in this paper. The model is based on the collocated,finite volume method with unstructured grids. One attractive feature of the model is that it has ability to handle arbitrary topology. The other is that horizontal mass and momentum flux across interface of cells is calculated by the Roe's Riemann approximation solver and the monotone,conservation scheme make a simulation results for keeping water balance in the entire computational field. The wetting-drying algorithm is also proposed to simulate flooding processes in sand shoal. To validate the model,the numerical simulation is performed for three cases:the wind driven circular flow,the dam-break wave on initial dry bed and the tidal flow in estuary of the Yangtze River. Results show that the model can accurately simulate the 3-D flow structure,and has good numerical stability.