In　order　to　study　seismic　behavior　of　the　pentagonal　cross-section　concrete　filled　steel　tube　(CFST)　mega-column　under　horizontal　loading　in　different　directions,　six　1/7.5　scaled　mega-column　specimens　were　designed.　The　section　constructional　details　of　the　specimens　are　divided　into　three　types,　including　one　cavity　with　steel　bars　inside,　four　cavities　without　steel　bars　inside　and　four　cavities　with　steel　bars　inside.　The　test　was　conducted　under　two　kinds　of　low　cyclic　loading　in　different　directions.　One　loading　direction　was　along　the　axis　of　symmetry　and　the　other　perpendicular　to　axis　of　symmetry.　The　failure　modes,　hysteresis　behavior,　bearing-capacity,　ductility,　stiffness　degradation,　and　energy　dissipation　were　analyzed.　Research　result　shows:　among　the　three　different　cross-section　types,　the　seismic　behavior　of　the　specimens　with　four　cavities　and　inner　steel　bars　are　the　best;　the　mechanical　property　of　pentagonal　cross-section　CFST　mega-columns　varies　obviously　in　different　directions,　hence,　the　balance　of　the　seismic　behavior　in　the　two　directions　should　be　considered;　as　the　yielding　story　drift　ratio　is　1/75　and　the　maximum　elasto-plastic　story　drift　ratio　reaches　1/24,　the　ductility　of　the　mega-columns　are　proved　to　be　perfect.