Computational methods have been successfully applied in structural analysis and drawings of large spatial structures. However, there are still huge challenges in performing conceptual design of structures using computers as what human brain is able to do. A computational method, named performance-based structural synthesis has been proposed and validated to generate and realize planar truss structures. However, it is insufficient for more general spatial truss structures whose geometries and load-carrying requirements are more complex compared with those of planar truss. Therefore, this computational synthesis method based on planar shape grammar was extended and presented in this paper to generate three-dimensional spatial truss structures through building 3D shape grammars and multi-objective hybridized optimization algorithm. Meanwhile techniques of load-generation were employed in the structural synthesis method to realize its engineering application. In the aspect of structural configuration, the method integrates structural topology, geometry and section size allocation; in the aspect of structural design and optimization, it takes into account the combining effects of safety, economy, construction and architectural elegance. Thus the structure generated by this synthesis method must be the best design in terms of the overall structural performance and cost compared with that obtained by traditional design method.