A transitional zone in landscape has a character of high spatial heterogeneity, from which demarcation lines are usually needed to be drawn for delineating various categories of landscapes and their extents. According to distinct differences of landscapes on both sides of the demarcation lines, and using GRID in ARCGIS, this paper provides a simpler and easier method based on cell-by-cell neighborhood processing. First it divides all the cells alternatively into two classes by an attribute, and then deduces which category the processed continuous or dispersive cells should belong to at random directions. And it sets a critical value according to location characteri stics of borderlines and double-handed attributes on classification. Then grid sclose to the demarcation line are selected by their short distance, because af ter neighboring processing, the closer grids have a higher attributive degree than the farther ones, and the discontinuous and lonely grids are abandoned so that the continuously distributed cells near the demarcation line can begot. After vectorization of grid layer, the line coverage can be used to select the demar cation line with the help of reference maps, such as hillshade or land use distribution maps. Taking the regions near the Capital, China, this paper gives defi nite mechanics of neighborhood processing, draws morphological boundaries out of landforms, checks accuracy of the method, and briefly discusses its meanings and availability. Also, it applies this method to other fields of landscape analy sis for application and validation. The neighborhood processing can trace the borderline between two classes of landscapes which are distributed complicatedly on two-dimensional space, and can be used to search the demarcation lines of agro-pastoral transitional zone, geomorphological demarcation line, or shoulder line of valleys on the Loess Plateau, etc.