Abstract: This paper mainly discusses the selection of target structures for large scale complicated engineering structures such as high-rise buildings and long-span spatial structures. A case-based-reasoning system based on self-organizing-feature-map(SOFM)is put forward to solve this decision problem. The case library is built by object-oriented method, and the desired structural styles are searched or matched by SOFM. An example, inwhich a high-rise building is studied, illustrates the working process of the system.