Base on ECOMSED model, a theree-dimensional hydrodynamic model is developed in the offshore area near the Changjing Estuary in the East China Sea. This model in driven by tide and wind,as well as inflow and outflowcurrents such as Kuroshio,Changjing runoff. The horizontal resolution is 1/20,°,. There have 11 layers on the verticaldirection. The numerical results of 4 main constituents of tide(M,2,S,2,K,1,O,1,)and currents are in good agreement with observation data. Compared with 20 gauge stations,the mean absolute erroe between the caluclated M,2, tidal amplitude and the observed oned is only 6.72cm; the mean absolute error of phased-lag is 5.23,°,.For S,2,the mean absolute errors of amplitude and phased-lag are 3.67cm and 7.21,°,respectively. The mean absolute errors of amplitude and phased-lag for K,1, are 3.25cm and 6.63,°, For O,1,the mean absolute error of calculation and observation is relatively small, amwith observation data measured during Aug., 2006 in the East China Sea.The correlation coeffiients of current between simulation and observation are greater than 0.75 generally. The three-dimensional hydrodynamic model develiped by this paper can well describe the characters of elevation and current in the offshore near the Changjiang Estuary and can be used as hydrodynamic background to simulate the suspend sediment transport in this sea area.