To　study　the　uniaxial　compressive　behavior　and　constitutive　relationship　of　high-strength　spiral　stirrups　confined　circular　ultra-high　performance　concrete　(UHPC)　columns,　an　experimental　investigation　was　presented.　In　this　research,　14　confined　UHPC　columns　and　seven　unconfined　UHPC　columns　were　tested　to　investigate　the　effects　of　the　stirrup　spacing,　stirrup　yield　strength,　and　steel　fibers　volume　content　on　the　compressive　behavior　of　the　UHPC　columns.　The　test　results　indicated　that　transverse　reinforcement　can　effectively　improve　the　deformation　capacity　of　the　UHPC　columns,　and　all　the　confined　UHPC　columns　showed　ductile　failure.　The　results　also　demonstrated　that　the　high-strength　stirrup　was　more　effective　than　normal-strength　stirrup　for　improving　the　post-peak　behavior　of　the　confined　UHPC.　Compared　with　the　stirrup　strength,　the　volumetric　ratio　of　transverse　reinforcement　had　a　more　significant　effect　on　the　post-peak　ductility　and　toughness　of　the　confined　UHPC　columns.　Transverse　reinforcement　and　steel　fibers　had　a　combined　effect　on　improving　the　post-peak　behavior.　Reducing　the　stirrup　spacing　or　increasing　the　steel　fibers　volume　content　can　better　improve　the　axial　compressive　behavior　of　columns.　A　new　constitutive　model　for　confined　UHPC　was　proposed.　Compared　with　four　existing　models,　this　new　model　was　in　good　agreement　with　the　experimental　curves.