Abstract: Rainfalls flow along the hypsography of the earth's surface,and valley elements such as the valley lines,catchment areas and naturally.Formed watersheds the research on the digital simulation of flow paths on the earth's surface is important for the digital watershed hydrological analysis.This paper puts forward the concept of the digital flow paths model by which we can get the flow path of any raindrop on the earth's surface.The contour lines and spaces are measured by the distance transformation of map algebra,and a method of building the digital flow paths model with the contour maps is advanced in the paper.The experiment result shows that the calculation of flow directions and flow paths can avoid the effect of the DEM elevation errors since the flow direction is calculated with distance transformation instead of D8 algorithm.Compared with the existing methods of the digital hydrological analysis,the method excludes the complex step of identifying and treating the depressions or flats in DEM.The model takes contour maps as original data and it can be availably applied in the extraction of valley lines,the delineation of catchment areas and the generation of watersheds.