Abstract: In this paper the dimensions and visualisation of spatial data are intro-duced.Two kinds of spatial data structures in 3D GIS are discussed.One is based on surface representation and the other is based on solid representation.Included are:boundary representation(BR),constructive solid geometry(CSG),non-uniform reasonable B-spline surface(NURBS),octree and tetrahedral irregular network. The characteristics and possible applications of these structures are also analysed.