The　mechanical　performance　of　reinforced　concrete　beam-thin-wall　joints　under　out-of-plane　bending　moments　is　studied　and　the　analytical　solutions　in　terms　of　stresses　and　rotational　stiffness　of　the　wall　are　obtained.　For　convenience,　the　equivalent　bending　width　of　the　shear　walls　is　introduced　and　obtained　based　on　two　equivalence　principles.　A　detailed　parametric　study　of　the　equivalent　bending　width　is　carried　out,　including　geometric　parameters,　boundary　conditions,　and　reinforcement　ratio　of　the　beam-wall　joint　in　shear　wall.　Some　simplified　formulae　for　the　equivalent　width　are　proposed　and　compared　with　both　the　analytical　solutions　and　the　experimental　results.　Good　agreements　are　found.　DOI:　10.1061/(ASCE)ST.1943-541X.0000519.　(C)　2012　American　Society　of　Civil　Engineers.