In order to stop the overall urban environment worsening and realize the harmonious and sustainable development between city and nature, how to protect and make use of mountains in city has increasingly become the focus point of planners. Yantai is a typical landscape pattern of the city, to protect the mountains have been damaged and improve the overall urban ecological environment, the plan took the way of delimiting the green line in the planning and implementation level. By using the GIS analysis method, drawing the line of natural mountain , the function line of ecological service for city and the line of management,then comprehensivly analysing the three lines, so as to obtain a reasonable mountain green-line in theory. On the basis, the theoretical line was finally revised to be an operable mountain green-line.