Abstract: A digital system for geological survey is described in this paper, which is based on teaching requirements of the Nanjing University field base for geological mapping in Chaohu，Anhui Province．Certain advanced techniques，such as GIS，RS and GPS have be en applied in the system．The powerful image manipulation and spatial analysis functions of GIS are fully used to generate the three-dimension digital map of geo logy for the study area ．The application of this system by students has greatly increased the efficiency of geo logical mapping in the field．