Abstract: In recent years, the water intake of a nuclear power plant in the north of Liaodong Bay, Bohai Sea, has been blocked several times by marine organism, resulting in the failure of the function of the cold source systems, and threatening unit safety. According to the actual situation of each water intake blockage event in the Nuclear Power Plant, the reason of blockage is analyzed, meantime the improvement measures and efforts in cold source guarantee system establishment and the control strategy of the Nuclear Power Plant are investigated and discussed. Finally, t the pending problems of the cold source is summarized, and the optimization in terms of water intake structure, how to cope with bad weather, strengthening monitoring and early warning are proposed,, to enhance the response capability of the Nuclear Power Plant to the outbreaks of marine organisms, and reduce the risk of water intake blockage.