Taking one tributary of tidal reach of the Yangtze river as typical example, according to the hydrological and pollutant transport characteristics of tidal rivers controlled by gate,the paper established a two dimensional dynamic hydrodynamic and mathematical model of heavy metals, simulated and analyzed the hydrodynamic rule of the tributary of the Yangtze river in the control of gate, and time varying characteristics and two-dimensional plane distribution of the concentration of heavy metal in the tributary with discharge of point source continuous.The simulation results show that under the influence of the tide and gate of the Yangtze river, the concentration of heavy metal in the tributary appears cyclical fluctuations in a certain range and with the trend of increase.Along with the elapse of sewage discharge time,The maximum concentration and fluctuation interval of heavy metals in river tends to be stable;in a typical super cycle,the spatial distribution of polluted area at low tide is more than that at high tide. The variation of heavy metals in tidal river is a very complex process.The simulation for this process can provide a technical basis for the management of river water quality and the prevention of pollution.