Abstract: Optimization algorithms are used usually to select the optimal structure from all alternative ones at the preliminary concept design stage for structural synthesis.For this aim,structural configurations must be described by shape grammar rules defined for the shape transform of truss structures.Based on the geometric constitution analysis and the re-classifying of spatial truss structures according to the property of geometric configuration,the characters of the classified structures were obtained.By extending shape grammars of planar truss with bracing system,the shape grammars of spatial truss structures were deduced successfully.In addition,the synthesis methods of all kinds of spatial truss structures were proposed.The results manifest that the incorporation between planar triangle rules and bracing system is equivalent to spatial polyhedron unit,and can be widely used to describe geometric configuration of spatial truss structures.