Abstract: Based on the real-time meteorological data, the hydrodynamic model in the coastal waters of the nuclear power plant was established and the model reliability was verified. Then a radionuclide diffusion model in the coastal waters of the nuclear power plant was established based on the Lagrange method. The hydrodynamic characteristics and radionuclide migration in the coastal waters of nuclear power plants were analyzed. The results show that the simulation hydrodynamic results in the coastal waters of the nuclear power plant can well depict the semi-diurnal tides in the coastal waters of the nuclear power plant. The basic radionuclide migration direction is from the nuclear power plant, along the coast, to the northeast direction. Influenced by the tidal current, the radionuclides advance in rotation. The surface radionuclides migrate along the coast with the shortest distance, and the middle radionuclides migrate with the farthest distance, and the bottom radionuclides migrate with the distance between surface and bottom radionuclides.