In this paper,based on the theory of structure logic paradigm,computational model ofsystem reliability is presented by using infimum operator and supremum operator corre-sponding concatenate and parallel systems respectively,which formed logical analysismethod for complex engineering system reliability. Employed this computational model,theoptimum design of engineering system reliability is solved successfully by using the multi-stage decision operator method.A numerical example computed of structure optimization oftruss is given in this paper.