Abstract: The foot of continental slope is an important terrain characteristic and is a basic evidence to get the out limit line of the expansion continental shelf right.Based on the ArcGis Engine platform,depended on our country multi－scales basic geography data and bathymetirc data,and strictly obeyed the United Nations article 76,the outside continental shelf slope point is gained according to seabed terrain data,then appropriate point is automatically choose to produce the foot line of continental slope.The research to the foot line of the continental shelf is very important for us to get the out limit line and regard our country.