This study introduces the application of 3D laser scanning on topography surveying for slopes, and the method of GIS-based 3D slope stability analysis. Operating the 3D laser scanning is both quick and safe. Compared to conventional surveying work, it can reduce surveying time and total workforce. The DEM data of slopes can be established in GIS from the high resolution ”point cloud” data obtained by 3D laser scanning. Therefore, landforms of slopes can be effectively captured for further slope analyses in GIS. This study developed a GIS-based 3D slope stability analysis program, called ”3D slope stability analysis modulus”. The modulus can compute a factor of safety for given slopes in GIS. After analysis of a scanned slope, the results of the factor of safety show the factor of safety for 3D analysis are larger than those of 2-D analysis and most of the 3D sliding surfaces searched by the modulus are close to those of the 2-D slide surfaces. It is also found that the selection of the width of a sliding surface for 3D analysis will influence the factor of safety in that increasing the width of a sliding surface will result in decreasing the factor of safety.