Abstract: In multi-scale display of vector data,it is very troublesome to decide the criterion of small objects,the sequence of scale values,and so on.In order to solve these key problems mentioned above,we discussed some key techniques and gave corresponding solutions.Based on the techniques discussed here,a demonstration was built.The experimental system used an extended GAP-tree index to realize the multi-scale display of vector data.The discussion about these key techniques problems will contribute to the research on the multi-scale display in GIS.