Topology　optimization　(TO)　has　been　proven　as　a　potent　tool　for　offshore　wind　turbine　supporting　structure　design.　Typical　TO　methods　optimize　the　material　layout　within　a　specific　and　fixed　design　domain　that　has　previously　been　established.　An　investigation　on　the　topology　optimization　design　of　jacket　structure　is　conducted　by　altering　the　design　domain,　which　is　expanded　by　adopting　two　strategies　of　extending　upwards　and　enlarging　the　distance　between　the　legs　at　the　bottom.　The　weighted　and　normalized　compliance　in　two　typical　loading　cases　is　adopted　as　the　objective　function　subject　to　available　material　usage.　The　checkerboards　are　suppressed　by　minimum　size　constraints　in　the　commercial　software　Optistruct　™,　and　geometrical　symmetry　is　imposed　to　assure　an　identical　material　layout　on　four　surfaces.　Two　sequences　of　innovative　designs　are　automatically　generated　by　the　proposed　strategies　including　expanding　the　leg　distance　and　extending　upwards　to　replace　portions　of　the　tower.　To　verify　these　optimized　results,　the　jacket　structures　are　reconstructed　based　on　the　initial　structures　and　force　transmission　paths.　Various　structural　responses　such　as　the　fundamental　frequency　of　the　entire　offshore　wind　turbine,　maximum　displacement,　and　pull-out　forces　are　investigated　and　analyzed　to　demonstrate　the　superiority　of　the　presented　approach　in　comparison　to　the　reference　structure.　The　effects　of　various　parameters　including　water　depth,　wave　height　and　system　damping　of　a　particular　optimized　structure　are　discussed.　The　resultant　trends　provide　several　suggestions　for　the　jacket　design.　©　2025