To　obtain　optimal　topology　shape　and　cables＇　pretension　force　for　prestressed　steel　structure,　a　mathematical　optimization　model　is　established　in　such　a　form　that　the　cables＇　pretension　force　and　the　structural　topology　are　referred　as　the　design　variables,　the　Von　Mises　stress　as　constrain　condition,　and　the　minimum　of　structural　weight　as　the　objective　function.　In　order　to　establish　the　model,　the　method　of　minimizing　structural　strain　energy　(maximizing　structural　stiffness)　is　applied　to　calculate　the　cables＇　pretension　force,　and　then　the　method　of　evolutionary　structure　optimization　is　provided　to　minimize　the　structural　weight　through　deleting　elements　with　minimum　Von　Mises　stress.　The　result　of　the　examples　coincides　with　corresponding　structural　performance,　and　this　indicates　the　method　in　this　paper　is　effective　and　efficient.