Abstract: In order to formulate the emergency response plan for the nuclear leakage accident in Haiyang Nuclear Power Plant, it is necessary to quickly predict the migration path and concentration distribution of the radio-nuclides in coastal waters. Firstly according to the real-time meteorological data, the radionuclide diffusion model of the nuclear power plant was established based on the methods of Lagrange and Euler respectively, and then the reliability of the model was verified. Secondly the radionuclide migration path and concentration distribution in summer and winter were analyzed. The results show that, due to the influence of the southeast wind and the ocean current in summer, the radio-nuclides of Haiyang Nuclear Power Plant migrate mainly to the northwest along the coastline. Due to the northwest wind and the ocean current in winter, the radio-nuclides migrate mainly to the east along the coastline, and then migrate to the southeast rapidly. In winter and summer, the radionuclide concentration in the coastal waters of the nuclear power plant decreases by about 9 orders of magnitude than the release amount after 5 days, and the radionuclide concentration decreases by about 10 orders of magnitude than the release amount after 10 days.