Yanchuan County of North Shaanxi Province,Niuchang of Southwest Guizhou Province,and Jingjing County of Hebei Province are selected as the typical areas of the loess landscape,karst landform,and hilly landform,respectively.DEM is taken as the research object in the three landform areas with spatial resolution of 5 m according to the map scale of 1∶10 000.Six slope algorithms to extract slope are used and comparison analysis is made to identify suitable algorithms for different landforms.Results show that the reasonable algorithms are three-order inverse distance square weight difference and three-order inverse distance weight difference.The accuracy of the algorithm using eight adjacent units is higher than the algorithm using two or four adjacent units.