Abstract: The coastal zone is not only a region with highly concentrated population and economy, but also a focus area of supervision of ecological and environmental fields. However, the criterion for delimitation of the coastal zone has not yet reached consensus over the world. Aiming at establishing a scientific and unified spatial standard boundary, and with idea of determining the landward boundary of coastal zone based on the ocean effect, the natural processes were selected including coastal erosion, rise of sea level, storm surge, extreme wind of typhoon, soil salinization, salinization and half-salinization of groundwater, and salty tide intrusion, in order to summarize the impact scope of these natural processes on the land. It was proposed that the landward boundary of coastal zone could be determined by the maximum impact width of the various processes. Take Tianjin coastal zone as an example, the land boundary of Tianjin coastal zone was delineated. It is recommended that the technical guidelines should be formulated to guide related provinces to delimit the landward boundary of coastal zone, and to coordinate a map of the landward boundary of coastal zone by the nation, thereby providing a unified spatial basis for the investigation, research, planning and supervision in coastal zone.