The　joint　core　area　is　always　casted　with　higher　strength　concrete　of　column.　The　sandwich　beam-column　joints　core　area　casted　with　weaker　strength　concrete　of　beam　can　simplify　the　construction　process,　but　the　seismic　performance　of　the　joint　is　impaired.　To　study　the　feasibility　of　the　sandwich　joint　improved　with　built-in　angle　iron,　one　unimproved　and　one　improved　3D　sandwich　joints　were　tested　under　bi-directional　reversed　cyclic　loads　with　constant　amplitude　to　investigate　the　seismic　behavior,　including　the　failure　mode,　ductility,　energy　dissipation,　stiffness,　strain　and　shear　strength.　The　test　results　show　that,　two　specimens　exhibit　joint　failure　after　the　beam　longitudinal　reinforcement　yields　in　the　joint　under　bi-directional　loads.　However,　the　enhancement　measure　increases　ductility　and　shear　strength,　improves　energy　dissipation,　stiffness　declination　and　deformation　capacity,　which　indicates　that　the　seismic　performance　of　sandwich　joint　is　improved.　Finally,　the　formula　is　presented　for　calculating　shear　strength　of　the　sandwich　joints,　and　the　solutions　agree　well　with　the　experimental　results　of　unimproved　and　improved　sandwich　joints.　©　2019,　Engineering　Mechanics　Press.　All　right　reserved.