One of the most severely eroded regions in the world is the Loess Plateau,where gully erosion is one of most important research topics.In order to estimate gully erosion from geographic perspective,Majiagou basin in Shaanxi Province as the study site was investigated using 5m×5m DEM as experimental data,combining three-dimensional analysis and data mining method in GIS,along with contour simplification techno-logy in traditional cartography.The results mainly show that terrain indicators changed by simplifing a group of contours that consist of a gully,which is equivalent to that gully was virtually filled in the laboratory.This method as virtual restoration of terrain can be used to simulate the formation and development process of a gully or a system of gullies in long terms.The concepts and methods developed in this paper may have some enlightening values to estimate total erosion of a gully or gully system precisely.