To　study　the　application　of　discrete　topology　optimization　methods　to　real　engineering　structures,　a　discrete　topology　optimization　method　for　the　optimal　design　of　multistory　steel　braced　frames　is　proposed　based　on　genetic　algorithm　and　evolutionary　structural　optimization　method.　By　using　topological　variables　and　modifying　elastic　moduli　of　useless　members,　a　uniform　mathematical　formulation　for　discrete　structural　topology　optimization　problems　is　presented.　The　given　formulation　is　applicable　to　truss　structures　as　well　as　frame　structures,　and　can　resolve　the　singularity　of　the　solution　in　the　topology　optimization　design　of　truss　structures　when　only　using　cross-sectional　areas　of　members　as　design　variables.　A　mixed　topology　optimization　method　for　the　large-scale　discrete　topology　optimization　problems　with　the　uniform　formulation　based　on　genetic　algorithm　and　evolutionary　structural　optimization　method　is　proposed　and　applied　to　the　topology　optimization　design　of　large-scale　steel　braced　frames.　Compared　with　genetic　algorithm　for　structural　topology　optimization,　the　mixed　topology　optimization　method　can　check　and　remove　the　redundant　elements　in　each　structure　generated　by　genetic　algorithm　by　using　the　evolutionary　structural　optimization　method.　A　numerical　example　of　3-bay　12-story　plane　steel　frame　with　bracing　system　shows　the　advantage　and　the　effectiveness　of　the　mixed　topology　optimization　method　proposed　for　the　layout　design　of　large-scale　multistory　steel　braced　frames.