Based on the development of modern technology, there is more and more application of GPS with the building of DEM on the research of gully erosion. The researches on gully erosion reflect the deeper understanding of erosion on the spatial scale. Complex morphology and topography have some special requirements on the building of DEM. This paper sums up the building of DEM, in which Arc/info is treated as the working platform. Meanwhile, combined with GPS sampling points in field and requirement of DEM building, preliminary discussion is performed on the application of GPS in field.