Several　issues　persist　in　the　design　and　construction　of　conventional　prestressed　concrete　encased　steel　(CES)　frame　structures.　This　includes　the　need　to　strengthen　the　steel　flanges　and　webs　during　the　passage　of　prestressed　tendons　and　longitudinal　reinforcements　through　the　joint,　and　insufficient　compaction　of　the　concrete　cast　in　the　joint　core.　Therefore,　a　novel　type　of　prestressed　CES　frame　structure　was　developed　using　concrete-encased　steel　angle　(CESA)　columns　to　replace　the　conventional　CES　columns.　To　investigate　the　seismic　shear　performance　of　this　new　type　of　prestressed　composite　joints　to　propose　a　method　for　predicting　the　shear　capacity　of　joint　cores,　this　study　performed　tests　and　nonlinear　analysis　on　three　prestressed　joints　and　one　nonprestressed　joint　under　low　cyclic　loading.　The　failure　patterns,　energy　dissipation,　stiffness　degradation,　deformation　recovery　performance,　and　ductility　properties　were　examined　for　these　joints.　The　effects　of　prestress　level,　axial　compression　ratio,　web　thickness,　stirrup　ratio,　and　steel　angle　ratio　are　also　discussed.　Two　formulas　are　proposed　to　predict　the　shear　capacity　of　joint　cores　based　on　the　fitting　of　tests　and　finite　element　analysis.　The　results　revealed　that　the　oblique　crushing　of　concrete　occurred　in　the　joint　core　at　the　peak　load,　resulting　in　shear　failure.　Increasing　the　thickness　of　the　steel　web　effectively　enhanced　the　horizontal　peak　load　to　increase　the　shear　capacity　in　the　joint　core.　However,　an　increase　in　the　axial　compression　ratio　may　reduce　ductility.　The　formulas　developed　to　predict　the　shear　capacity　of　the　joint　core　exhibited　much　higher　accuracy,　where　the　simplified　practical　formula　can　facilitate　convenient　design　implementation.　Overall,　these　findings　demonstrate　excellent　seismic　shear　behavior　for　prestressed　composite　joints　while　providing　technical　support　for　applications　in　such　types　of　prestressed　frame　structures.