The earth's surface erosion by runoff is essentially a result from gravitational potential energy of running water.Started with energy accumulation of slope running water, basic concepts and computational principles of the potential factor for running water erosion reflecting erosive power of original slope were presented.Algorithm of the computation for the potential factor was designed based on the high precision DEM, computation of the potential factor was completed for a simulated multiphase watershed, and the re-sult corresponding to erodent power points was acquired based on the potential factor. The spatial distribu-tion characteristics of erosive power points were analyzed and then, some preliminary discussions on the evo-lution of topography were made.Results showed that the research on slope erosion degree and its evolution in use of the potential factor is of theoretical significance and practical value.