The Geological Spatial Information System is a tool for managing, analyzing and processing geological spatial data. As a spatial information system, GSIS is somewhat similar to GIS, therefore the basic theory and implementation techniques of GIS can be used in GSIS. However, GSIS has its own characters, and cannot be completely realized by just using the existing GIS software. GSIS is still a developing system, but it can be widely used in geological study, and will play an important role in promoting the development of geology. This paper introduces a framework of GSIS based on the distributed system, which provides three-dimensional spatial data creation and management, data-object model management, multimedia data storage and query, blurry processing and expert-system functions.