On the basis of analyzing the structure of the optimal models for complex machines

and discussing the coupling elements that affect the structure

a set of appropriate solutions is presented.By discussing the technologies of multidisciplinary optimization

the complex machine is divided into two hierarchical optimal models.The lower level is the functional level(i.e.sub-systems);the upper level is the systematical level for communication among the sub-systems and moderating couple elements.In results

the structures of the optimal models for the sub-systems and the systemic level are given

and the classification and features of the couple elements and solution methods are designed.The above modeling theories and the model structures solve the difficulties of the optimal modeling for the complex machines

such as the large models

and the complex relation of the design functions and variables.