Abstract: This paper firstly analyzes the incomplete-controllability of space manipulators in configuration space. Based on the analysis,a hierarchical quantization modelling method of configuration space suitable for space robots is presented. The presented method firstly hierarchically quantizes the configuration space, then builds up the Configuration Space Graph(CSG) by defining the adjacent relations between configurations. The collision situations of vertices and edges of CSG are defined. Finally for a space robot model,an example of configuration space modelling as well as a motion planning result based on the modelling method are given.