Based on the topological theory

this paper studied a new approach named"Node Searching" for transferring raster to vector. The main advantages of the new approach were: (1) high efficiency and high speed;(2) capable of building topological structure of vector data automatically during converting; (3) unnecessary to process raster data before converting; (4) not very sensitive to the number of raster image's column and rows. It was proved to be a good approach in experiments.