A 2-D mathematical model with multiple nested grids of tidal current and sediment in estuary was set up. With the help of this model, the flow and sediment transport field near the artificial island of south fort in eastern Hebei province was simulated. It was concluded from the flow field simulation that the current velocity decreased at the back of the island and at each side of the approach bridge as a result of their interception effect,and increased in front of the island for its deflecting effect. In addition, the hydrodynamic conditions at different part of the sand digging pools also revealed various characteristics because of the changes of topography. The results of the simulation of sediment field coincided with the influence of hydrodynamic conditions change on sedimentation: siltation happened where flow strength decreases, while erosion happened where flow strength increases.