Abstract: The Law of Topographic Mapping of China stipulates that the mapping on land should cover the area above the average high tide under the supervision of the local governments,while the mapping of offshore area covers the area below the average low tide under the supervision of the navy.But no one is responsible for the mapping in the zone between the average high tide and low tide,where most of the islands and reefs occur.This paper deals with the transfer of the mapping results during the high and low tides and the way to satisfy the requirement of publication and serve the needs of GIS database,display and data analysis.