Abstract: Two main cooling methods, i.e. once-through cooling and secondary circulation cooling, currently applied in coastal nuclear power plants and their characteristics are introduced, and the drainage engineering environment and economic effect induced by using these two cooling methods are analyzed, which include subsurface pipe drainage and open channel drainage and their advantages and disadvantages as well. In addition, a comparative analysis is carried out by combining the comparison and optimization of the cooling method and drainage scheme of a nuclear power project in Shandong. The results demonstrate that after using the secondary circulation cooling system the volume of warm-water discharge is significantly less than that by using the once-through cooling method and the area of 4 ℃ temperature rise envelope is only 3% of the sea area used by the once-through cooling scheme. This not only makes the sea area used by warm-water drainage reduce significantly, but also greatly reduces the loss of marine organisms caused by the water intake and drainage of the nuclear power plant, meeting the requirements of saving and intensive use of the sea of the project. Therefore, it can effectively reduce the impact of coastal nuclear power plant on marine ecological environment and realize a harmonious development of economy, society and environment to use the secondary circulation cooling method and its drainage engineering optimization scheme in the coastal nuclear power plants.