China is located between the circum-Pacific seismic belt and the Mediterranean-Himalayan seismic belt, the tectonic activity in both the land and sea areas is very strong. With the continuous and rapid development of coastal economy, especially the strategic conception of “21st Century Maritime Silk Road” proposed, the seismic fortification of coastal, offshore and marine engineering has become an issue of concern in the field of earthquake science. Therefore, it is urgent to carry out seismic zoning in sea areas to provide the basis for seismic fortification. The project of the “Research on key technologies of seismic zoning in sea areas” supported by the National Key R&D Program of China (2017YFC1500400), takes the basic principles, scientific issues and key technologies of seismic zoning in sea areas as its research objectives, puts forward the principles for the compilation of China seismic zoning map in sea areas, forms zoning methods and technical system, and then provides technical support for the compilation of seismic zoning map of China in sea areas through the demonstration and application of seismic zoning in typical sea areas. After two years of project research, the active tectonic framework maps of the eastern and southern seas of China and seismic tectonic maps of three typical sea areas (located in the Yellow Sea, Taiwan Strait and South China Sea) were compiled, and seismic models of subduction zones in China sea and adjacent areas were obtained; A unified seismic catalogue of China sea and adjacent areas was established, and the seismicity scheme and parameters of offshore seismic zones of the continental shelf of China were given; The differences of strong motion characteristics in land sites and seabed sites and from inland earthquakes and subduction earthquakes are statistically analyzed, and a scheme for the establishment of seismic ground motion attenuation model was proposed based on observation records and seismic simulation results of ground motion; Models of seabed topographies and seabed sites in China sea and adjacent areas were established, and a preliminary seismic ground motion adjustment method for the effect of sea site was given; The seismic response analyses for the structures of the marine engineerings, such as offshore wind powers, bridges and submarine pipelines, and the coral islands were carried out respectively, and the sensitivity of the seismic response of marine engineering structures and coral islands to different seismic ground motion parameters were given; the division scheme of seismic belts and potential source zones in the typical demonstration areas were proposed, and the principle and method of seismic zoning in sea areas were formed, and design of the technical framework of seismic zoning in sea areas was completed.