The optimized section area considering reliability is in some degree different from that without it , which can be applied in practice . the examples of three bar truss and parallel chord truss with biggish span are analyzed on the conditions of reliability or not , the results of which prove the model and method proposed in this paper are feasible 本文分別從考慮可靠度約束和不考慮可靠度約束的情況下對三桿桁架,和跨度較大的平行弦桁架進行算例分析;并將兩種算法結果進行比較,結果證明本文模型與方法是可行的和現實的。