Abstract: Formal description and representation of topological relationships between 3D spatial features is one of the key issues in developing 3D GIS. An approach was proposed in this paper to describe the topological relationships between 3D spatial features with their k-simplex components (0≤k≤3). The topological relationships for the pair of k-simplex were examined with dimension extend 9-intersection. Six types of primitive relations were used, such as touch, cross, in, disjoint, overlap and equal. The topological relationships between 3D spatial features were described with a topological matrix T which compared the relationships between any two k-simplex of the two 3D spatial features.