Abstract: The numerical models of tidal current and suspended sediment concentration of the Yangtze River estuary were established based on ECOMSED model.The verification of the models shows that they are effectively for simulating tidal current and suspended sediment distribution in the Yangtze River estuary.The models were then used to simulate the hydrodynamic and distributionsof sediment before and after the north branch narrowing in the north branch of Yangtze River estuary.The numerical result shows that, after the north branch narrowing, the channel and the mouth of the north branch would be narrowed significantly, and tide would be weakened and water level would also be reduced, and tide current would be increased due to the narrowing of channel in the north branch.The numerical results also show that the concentrations of suspended sediment in the north branch would be reduced along with the reduce of tide.The north branch narrowing in the Yangtze River estuary would influence the tide current and suspended sediment concentration in the north branch, and it has little impact on the water level and tide current, and suspended sediment concentration in the south branch and the estuary area.