This　paper　proposes　a　topology　optimization　methodology　for　offshore　wind　turbine　(OWT)　jacket　structure　design　in　the　concept　phase.　First　of　all,　modal　analysis　and　load　calculation　of　a　5　MW　reference　OWT　are　performed.　On　the　basis　of　finite　element　analysis,　the　displacement　and　von　Mises　stress　of　multi-jacket　support　structures　in　various　ultimate　loading　conditions　are　explored.　Furthermore,　structural　topology　optimization　formulation　aims　to　minimize　a　weighted　normalized　objective　for　the　OWT　jacket　structure.　Therefore,　several　optimum　structures　are　obtained　by　adjusting　weighting　coefficients.　For　the　coupling　effect　between　the　structure　and　applied　load,　load　recalculation,　displacement,　and　stress　reanalysis　are　performed　on　the　jacket　structure　based　on　the　topological　configuration　under　a　specific　weighting　factor.　Comparisons　are　made　be-tween　the　reference　structure　and　optimized　structure.　Without　the　addition　mass,　the　fundamental　natural　frequency　of　the　optimized　structure　is　marginally　increased,　but　the　maximum　displacement　and　von　Mises　stress　are　drastically　lowered,　indicating　that　the　optimized　structure　outperforms　its　reference　counterpart.　These　findings　conclusively　demonstrate　that　the　proposed　TO　technique　for　the　design　of　OWT　jacket　structures　is　feasible　and　preferable.