Abstract: Based on analyzing the display characters of basic electronic map,and considering the effects of multi-factors,this paper proposes the concept of electronic map displaying scale and multi-scale displaying model.Then a method of calculating the electronic map load was proposed.After this,it discusses the keystone and method of ensuring key scale based on feature point in the map load curve,and analyzes the error in this model.Finally,it establishes multi-scale display classification system of national boundary electronic map.Based on this,multi-scale display national boundary electronic map is undertaken in electronic map display system,which achieves a better effect and proves the feasibilities of this method.