The impact on the environment of radionuclide release from nuclear power plants has attracted increased attention, especially after the accident at Fukushima Daiichi Nuclear Power Plant in Japan. Based on the mechanisms of adsorption/desorption at solid/liquid interfaces and a surface micromorphology model of sediments, a theoretical expression of the distribution coefficient Kd is derived. This coefficient has significant effects on the distribution of radionuclide in seawater, suspended sediment and seabed sediment. Kd is then used to simulate ⁹⁰Sr transport in the sea near the Daya Bay Nuclear Power Plant. The simulation results are compared with field measurements of tidal level, current velocity, suspended sediment concentration and ⁹⁰Sr concentrations in the same period. Overall, the simulated results agree well with the field measured data. Thus, the derived expression for Kd is capable of interpreting realistic adsorption/desorption processes. What’s more, conclusion is drawn that about 40% ⁹⁰Sr released by Daya Bay Nuclear Power Plant will be adsorbed by suspended sediment and 20% by seabed sediment, only about 40% ⁹⁰Sr will remain in the sea near Daya Bay Nuclear Power Plant in South China Sea.