Abstract: There have been a number of marine biological outbreaks in coastal nuclear power projects in China, which lead to exception of water intake system of nuclear power plants. Nuclear plants carry out marine ecological investigation at the feasibility study stage. At present, the investigation and evaluation of marine organisms in the early stage of nuclear power plant construction are lack of pertinence to the marine organisms causing disasters. In this paper, the actual work feedback of disaster causing marine organisms and nuclear power plant cold source safety has been combined. The deficiencies of marine biological investigation in the early stage of nuclear power project construction are analyzed and the optimization measures of investigation scheme are provided. To try to enhance the relationship between marine biological investigation and the defense system of NPP’s cold source safety in depth.