Impacts　have　the　distinctive　characteristics　of　diverse　conditions,　low　frequency,　repeated　occurrence,　and　high　hazard;　as　such,　they　have　emerged　as　a　leading　factor　in　bridge　collapses.　Ultra-high-performance　concrete　(UHPC)-filled　high-strength　steel　tubular　members　are　the　preferred　choice　for　large-span　and　high-pier　bridges　whose　vulnerability　to　impacts　cannot　be　ignored.　Nine　UHPC-filled　high-strength　square　steel　tubular　specimens　were　designed　in　this　study　to　explore　their　axial　impact　resistances　and　residual　bearing　capacities　using　a　drop　hammer　and　a　hydraulic　testing　machine,　respectively.　The　influence　of　impact　energy　and　UHPC　steel　fiber　content　on　key　performance　indicators　including　impact　force,　deformation,　energy　absorption,　residual　capacity,　and　residual　rate　were　subsequently　evaluated.　The　results　show　that　the　impact　resistance　and　residual　capacity　of　a　UHPC-filled　high-strength　steel　tubular　member　are　significantly　higher　than　those　of　a　high-strength　concrete-filled　high-strength　steel　tubular　member　and　that　UHPC　members　can　withstand　greater　levels　of　axial　impact　energy.　Furthermore,　the　strong　bonding　behavior　between　the　steel　fibers　and　concrete　matrix,　as　well　as　the　resulting　fiber　network　skeleton,　can　effectively　improve　the　strength,　crack　resistance,　ductility,　and　energy　dissipation　capacity　of　UHPC.　Indeed,　the　incorporation　of　steel　fibers　significantly　reduces　the　peak　displacement　and　residual　deformation　of　components　subjected　to　axial　impact　by　up　to　14.　3%　and　31.　4%,　respectively,　and　an　increase　in　steel　fiber　volume　content　from　0%　to　2%　increases　the　energy　absorption　per　unit　deformation　by　38.　4%.　In　addition,　when　a　specimen　does　not　suffer　severe　damage　from　the　axial　impact,　its　residual　bearing　capacity　and　residual　rate　increase　significantly　by　up　to　28.　3　%　and　12.　4　%,　respectively.　Therefore,　an　appropriate　increase　in　fiber　content　(up　to　2　%)　can　improve　the　axial　impact　resistance　and　residual　bearing　capacity　of　a　UHPC-filled　high-strength　square　steel　tubular　member.　However,　the　steel　fiber　contents　considered　in　this　study　align　with　conventional　engineering　practice,　and　a　more　comprehensive　assessment　and　analysis　should　be　conducted　for　scenarios　beyond　this　scope.　©　2024　Chang＇an　University.　All　rights　reserved.