This　paper　is　engaged　in　the　study　of　a　partially　encased　steel-concrete　composite　beam　with　web　opening　(PECBWO).　PECBWO　refers　to　a　web　opening　in　a　wide　flange　H-beam　or　I-beam　and　then　filling　the　web　with　concrete,　with　the　concrete　remaining　equally　cellular.　This　specimen　is　superior　to　conventional　cellular　beams　and　partially　encased　concrete　beams　(PECB),　saving　on　casting　formwork　and　structural　self-weight.　This　test　focuses　on　the　flexural　performance　of　the　PECBWOs.　The　parameters　of　the　PECBWOs　studied　are　concrete　strength,　opening　shape,　opening　ratio,　and　thickness　of　the　bottom　flange　of　the　steel.　For　this　purpose,　seven　PECBWOs　were　designed　for　flexural　tests　and　one　solid　web　partially　encased　beam　(PEB)　was　used　as　a　control　group.　The　analysis　of　the　damage　pattern,　load-deflection,　strain　distribution,　bearing　capacity　and　ductility　of　the　eight　specimens　subjected　to　bending　was　carried　out　by　obtaining　load-displacement　curves　and　strain　data　of　the　section　steel　through　test　practice.　The　results　show　that　the　PECBWO　with　14.9　%　opening　ratio　and　circular　openings　have　the　excellent　performance,　with　cracking　load　and　flexural　capacity　similar　to　that　of　solid　web　PEB,　and　possess　better　seismic　performance　with　41.6　%　increase　in　ductility.　In　addition　the　bottom　flange　of　the　steel　is　equivalent　to　the　tensile　reinforcement　of　the　reinforced　concrete　beam,　and　the　reduction　of　the　thickness　of　the　bottom　flange　significantly　reduces　the　flexural　capacity　and　ductility　of　the　PECBWO.　For　the　same　case,　the　specimen　with　C50　has　a　higher　crack　load.　An　analytical　model　for　flexural　load　bearing　capacity　was　also　provided.　©　2024　Institution　of　Structural　Engineers