Digital　City　is　the　digital　technical　service　system　which　is　synthetically　applying　such　as　Geographical　Information　System　(GIS),　Remote　Sensing　(RS),　Satellite　Positioning　System,　Computer　Network,　Multimedia,　Virtual　Simulation　and　so　on　many　kinds　of　technical　methods,　automatically　gathers　and　dynamically　manages　City＇s　infrastructure,　function　mechanism,　and　at　last　assists　Decision-making　Supports.　The　Three-Dimensional　Urban　GIS　(3D　UGIS)　is　the　key　supporting　technology　of　the　Digital　City,　and　also　needs　certain　key　technology　to　support　it.　Such　as　building　3D　Spatial　Data　Model,　huge　spatial　data＇s　storage　method　in　spatial　database,　and　reconstructing　3D　virtual　scene.　And　this　thesis　precisely　centers　on　these　key　problems　to　launch　research.　©　(2012)　Trans　Tech　Publications,　Switzerland.