High resolution DEM(Digital Elevation Model, DEM) is created based on original CAD terrain map (one reservoir as example). Then the article offers precision analysis、topographic factors analysis、visibility analysis、reservoir volume and submerging acreage computing. Then adopting GeoVRML technique is to implement the functions of WebGIS 、visualization and query of computing result、graph data visualization and reservoir region virtual scene roaming etc. The system implements deep administrative levels information diged and long-distance visualization expression. The result shows on the basic high resolution DEM to realize 3-Dimensional Visualization Analyse and calculation functions and compress the spatial data to release these data in the WebGIS(Web Geographical Information System, WebGIS) as well as.