Abstract. Aiming at influence of discharge thermal water from the Huarun Caofeidian power plant, a 2D hydrodynamic model was used to simulate the tidal current field of waters receiving residual chlorine in discharged thermal water in Caofeidian Coastal Area. With the computed tidal current field considered to be the hydrodynamic conditions of the residual chlorine transport simulation, the concentration distribution of the residual chlorine was predicted with a 2D convection diffusion model and its effect on the marine organisms was analyzed. The results show that, the area affected by residual chlorine water is 0.14 and 0.21km 2 respectively in winter and summer. The residual chlorine concentration around the outfall is lower than most of the safety concentration for shellfish and Copepods. In winter and summer, some fish avoided reaction to the residual chlorine which area is 0.83 and 1.43km 2 respectively.