The invention relates to a method for the automatic vectorization of a road network digital raster map in the technical field of image processing. Firstly, the road network digital raster map is read into a computer memory, a road crossing on a road network image, which comprises a crossed road crossing and a road terminal, is detected, and pixels consisting of the road crossing are marked; secondly, each road crossing is used as a center to detect an adjacent road crossing, a pixel chain from the road crossing to each adjacent road crossing is formed simultaneously, and nodes are added at intervals to each pixel chain, thereby obtaining pattern points recording the shape of a road; and finally, redundant nodes which are added in the step two are deleted, and a vectorization result is preserved according to the normal vector map format. The road network vector digital map formed by the invention can bring great convenience for the operation of locus correction of an intelligent transportation system and a vehicle navigation system.