Abstract: In this paper, the definition of the boundary of the coastal zone is reviewed from the perspectives of geography, geology and socio-economic radiation range, and the idea of determining the boundary from the perspective of the coastal zone function is put forward, and based on the function of ecological barrier of the coastal zone, the method of the boundary delineation of the coastal zone has been preliminarily analysed and discussed. and discussion. In view of the ecological barrier function is the focus and point of attention for carrying out ecological protection and restoration of the coastal zone in China, this paper proposes that under the function orientation of ecological barrier, the scope and boundary of the coastal zone should be divided on the basis of the following: the land area should take the scope of all kinds of protected areas and coastal protection forests as the boundary standard of the landward side of the coastal zone and define the landward side of the coastal zone by combining with the areas of human activities and islands, etc. The sea area is defined on the basis of the outbreak areas of marine biological disasters such as algal tides, and the boundaries of typical marine ecosystems such as mangrove forests, seaweed farms, seagrass beds, oyster reefs and coral reefs. And at the same time, the seaward boundaries of the coastal zone are comprehensively demarcated by taking into full consideration the needs of the special paths of migratory birds in coastal zones such as estuaries and islands. We would like to discuss this issue and provide useful ideas for the scientific delineation of the coastal zone in China.