Abstract: In the environmental impact assessment process of northern nuclear power plant construction projects, the influence of icing conditions on the water temperature rise is not considered in the numerical simulation analysis of thermal discharge, which leads to the conservative and uneconomical selection of water temperature rise. To explore the temperature rise and ice melting characteristics of thermal drainage from nuclear power plants in cold regions, a three-dimensional tidal current field and thermal drainage model are established including the thermodynamic process of air-sea ice interface heat flow, sea ice internal heat conduction, sea ice-ocean interface heat flow, and sea ice generation and dissipation. Taking Xudapu Nuclear Power Plant as an example, the diffusion law and melting range of thermal drainage with ice effects are studied. The results show that the maximum temperature rise envelope area affected by sea ice with a surface temperature rise of 0.5 ℃, 1.0 ℃, and 2 ℃ during the spring tide is reduced by 38.93%, 32.18%, and 3.72%; respectively, compared to those without sea ice effects; And the melting range caused by the temperature drainage during the simultaneous operation of Units 1-6 is 36.31% larger than that during the simultaneous operation of Units 1-4. In addition, the working conditions dominated by concealed pipe drainage are opposite to those dominated by open channel drainage. As the drainage source is closer to the bottom layer, the maximum temperature rise envelope area of the surface, middle, and bottom layers increases sequentially. This study can provide a new method for environmental impact assessment of nuclear power plants in cold regions.