Abstract: In environmental hydrodynamics, the release of pollutants from sediments is one of the main problems. Under the condition of hydrodynamics, the resuspension of polluted sediment makes a large number of pollutants released again, resulting in the secondary pollution of water body. Based on a large number of experimental data provided by water channel experiments, a coupled mechanical model of overlying water body, sediment and pollutants is established in this paper. The process of sediment incipient motion and pollutant release are numerically simulated under different velocity of overlying water. The quantitative relationships among velocity, particle volume fraction, pollutant concentration, turbulent kinetic energy and time are obtained by analyzing the relationship between flow field characteristics and pollutant concentration distribution. The results show that the pollutants release process of sediment resuspended is a coupling process composed of overlying water, sediment and pollutants. When the sediment particles are resuspended into the overlying water body, the flow characteristics of overlying water and the release of pollutants are affected rapidly. For the non-adsorption pollutants, the complex characteristics of flow field are the main factors affecting the release of pollutants from resuspended sediment. When the flow field characteristics (Re) change, the contribution of convection diffusion and turbulent diffusion is different to pollutant release process. The coupling model of overlying water body, sediment and pollutants is established, and the quantitative relationship between hydrodynamic conditions and sediment pollutant release is studied, which can provide support for the construction of water pollution model in lake and reservoir area.