Abstract: A novel method for automatic connection of Loess shoulder-lines using improved Snake model is designed in this paper.Firstly,according to the morphological characteristics of loess hillslope,raster points on the position of shoulder-lines are detected based on high resolution DEM data.Then buffer curve of divide line sets as the initial Snake curve.Thirdly,the gradient vector flow field,as core parameter in Snake model,is modified by hillslope flow direction field.Finely Snake curve is forced to creep to shoulder-line points under the guidance of the modified Snake model to make a continuous shoulder line,which is the division of P-N terrains.Segmentation experiments show the continuity and precision of results meet our need and have good agreement with the real topography.