Sugar　cane　bagasse　ash　(SCBA)　is　the　final　waste　material　in　the　sugar　production　chain.　Due　to　the　pozzolanic　characteristic　and　the　abundance,　SCBA　has　been　tried　to　utilized　in　construction　materials.　In　this　study,　ecofriendly　ultra-high　performance　concrete　(UHPC)　was　developed　with　SCBA　as　a　cement　replacement.　The　effects　of　SCBA　on　the　fluidity,　setting　time,　compressive　strength,　flexural　strength　and　autogenous　shrinkage　of　UHPC　were　analyzed.　Hydration　heat　evaluation,　X-ray　diffraction　(XRD),　thermogravimetric　(TG)　analysis,　and　mercury　injection　(MIP)　were　applied　to　reveal　the　effects　of　SCBA　on　cement　hydration,　hydration　products　and　pore　structure.　The　results　indicate　that　the　application　of　SCBA　in　UHPC　as　a　cement　replacement　not　only　maintains　the　compressive　strength　but　also　improves　the　workability　and　decreases　the　autogenous　shrinkage　of　UHPC　paste.　Compared　to　the　control　group,　UHPC　prepared　at　a　40%　replacement　rate　obtained　a　good　comprehensive　performance.　Autogenous　shrinkage　decreased　by　24.48%,　and　the　compressive　strength　was　almost　the　same　as　that　of　the　control　group.　This　study　verifies　the　technical　feasibility　of　SCBA　application　as　a　cement　replacement　in　UHPC　and　may　further　promote　the　utilization　of　agricultural　byproducts　in　cementitious　materials.