This　study　investigated　the　flexural　behavior　of　rectangular　ultra-high　performance　concrete-filled　high-strength　steel　tube　(CuFTh)　members.　A　total　of　11　tests　were　conducted.　The　influence　of　yield　stress　of　steel　(Fy),　steel　fiber　volume　content　of　UHPC　(&　rho;),　height　(H)　of　steel　tube,　and　thickness　of　steel　tube　wall　(t)　was　investigated.　3D　finite-element　models　were　developed　and　benchmarked　to　conduct　parametric　studies.　Results　from　the　experimental　tests　and　FEM　analyses　indicated　that:　(i)　Fy,　t,　and　H　have　a　significant　influence　on　the　flexural　strength,　while　the　compressive　strength　of　concrete　has　a　negligible　impact;　and　(ii)　increasing　&　rho;　slightly　improves　the　flexural　strength,　but　obviously　reduces　the　ductility.　Additionally,　results　from　the　experimental　tests　and　FEM　analyses　were　compared　with　the　strength　estimated　using　AISC　360-16,　GB　50936-2014,　Eurocode　4,　and　AIJ.　The　comparisons　showed　that　Eurocode　4　and　AISC　360-16　can　reasonably　estimate　the　flexural　strength　of　rectangular　CuFTh　members.　AIJ　is　recommended　for　predicting　the　service-level　flexural　stiffness　of　rectangular　CuFTh　members.