In　this　study,　the　influence　of　the　slenderness　and　diameter-thickness　ratio　on　the　interfacial　bonding　performance　of　hollow　steel　tube　and　Ultra-high　toughness　cementitious　composite　(UHTCC)　was　analysed　by　conducting　push-out　test.　The　study　examined　the　specimens＇　failure　modes,　strain　distribution　curves　along　the　longitudinal　direction　of　the　steel　tube,　load-slip　behaviour,　and　interfacial　bonding　mechanisms.　A　finite　element　model　was　developed　and　validated　against　experimental　findings.　The　results　indicated　that　neither　the　hollow　steel　tube　nor　the　UHTCC　reached　their　respective　yield　strengths　during　testing.　The　strain　on　the　inner　surface　of　the　steel　tube　increased　with　increasing　load.　The　interface　load-slip　curve　revealed　distinct　cementation,　slip,　and　friction　phases.　The　stress　distribution　and　load-slip　characteristics　of　the　steel　tube　simulated　via　finite　element　analysis　closely　match　the　experimental　outcomes.　Subsequently,　considering　the　influence　of　the　steel　tube　length　and　diameter,　a　statistical　regression　analysis　was　performed　to　determine　the　bond　strength　and　bond　failure　load　of　the　hollow　steel　tube　and　UHTCC,　yielding　calculation　formulas　correlating　these　parameters　with　the　slenderness　and　thickness　ratios.　An　error　analysis　validated　the　derived　formulas　against　experimental　and　simulation　results.　Furthermore,　two　variables,　namely　the　shear　modulus　of　the　bonding　layer　and　the　wall　thickness　of　steel　tubes,　were　introduced　for　the　finite-element　simulation　under　linear　elastic　conditions,　and　the　changes　in　the　related　properties　of　the　hollow　steel　tube　and　UHTCC　members　in　response　to　the　variation　of　some　factors　were　discussed　and　analysed.