In　this　study,　the　cooperative　working　mechanism　of　high-strength　steel　and　ultra-high　performance　concrete　(UHPC)　was　investigated.　Five　UHPC　columns　were　tested　under　reversed　loading,　including　three　UHPC　columns　reinforced　with　high-strength　steel,　one　UHPC　column　reinforced　with　normal-strength　steel　and　one　UHPC　column　reinforce　with　normal-strength　steel　and　confined　by　carbon　fiber　reinforced　polymer　(CFRP)　sheet.　The　results　show　that　all　the　columns　failed　in　bending　mode.　High-strength　reinforcement　can　restrain　UHPC　effectively　and　improve　the　initial　stiffness,　ductility　and　bearing　capacity　of　the　test　columns.　The　larger　stirrup　spacing　can　result　in　earlier　cracking　and　lower　the　bearing　capacity　of　the　test　column.　The　CFRP　sheet　can　provide　effective　confinement　for　the　UHPC,　which　can　improve　the　yield　and　ultimate　displacement　of　the　test　columns.　However,　it　has　little　contribution　to　the　bearing　capacity.　A　flexural　model　has　been　developed　for　the　analysis　of　UHPC　bending　members,　and　the　results　from　the　model　are　in　good　agreement　with　the　experiment　data.