To　examine　how　different　compositions　and　shapes　of　steel　fibers　influence　the　mechanical　responses　and　damage　behavior　of　ultra-high　performance　concrete　(UHPC),　several　axial　compression　tests　are　performed.　The　impact　of　steel　fiber　on　acoustic　emission　(AE)　parameters　of　UHPC　is　studied　based　on　the　AE　technology.　The　variation　law　of　AE　parameters　during　damage　evolution　is　qualitatively　analyzed.　According　to　the　development　trend　of　AE　energy　and　cumulative　energy,　the　damage　level　of　specimens　is　quantitatively　investigated.　The　damage　constitutive　equation　of　UHPC　is　established　based　on　the　AE　energy.　The　results　show　that　steel　fiber　is　beneficial　to　the　strength　and　ductility　of　UHPC.　The　development　trend　of　AE　accumulative　ringing　count　and　accumulative　energy　show　a　similar　growth　rule　with　strain　and　have　a　good　correspondence　with　the　stress-strain　curve.　The　damage　evolution　model　based　on　AE　energy　and　accumulative　energy　fits　well　with　the　test　data,　which　can　quantitatively　analyze　the　damage　level　of　UHPC　under　axial　compression.