Abstract: Based on Aulti-level optimization theory,a reliability-based optimum strategy is presented to solve the large-scale structure problem. The main idea is that the optimum distributions of structural reliability design index and weight design index are involved in the optimization Process from the conceptual design. A large-scale structure is decomposed into a multi-level substructure system, in which the reliability-based optimum solution of the lowest-level sub-structures can be obtained by the present met...