Abstract: Slop length is one of the most important terrain factors in the quantitative assessment research of regional soil and water conservation.Taking Xiannangou watershed area in loess plateau region for example,DEM data with 5~100 m resolution is established based on 1∶10 000 digital topographic maps using ANUDEM software,and the surface of slop length was extracted by LS_TOOL,to analyze the changing regularity of slope length with DEM resolution.The results indicated that the slop length values of these terrain feature points are changing regularity with DEM resolution reduction.The changing regularity of mean slop length in different classifying areas appears difference,and the area ratio is increasing in all classifying areas except the 100 m.The mean slop length of Xiannangou watershed is expanded with DEM resolution reduction,and the short slope length is decreasing and the long slope length is increasing.The mean value appears linear growth with DEM resolution variation.

Key words: DEM, Resolution, Slope length, Terrain feature point, Slope length classifying area