The　anti-seismic　capability　of　beam-column　joints　in　reinforced　concrete　frame　structures　undergoing　bidirectional　loading　may　be　lower　than　the　designed　capability　for　unidirectional　earthquake　action.　To　date,　detailed　calculation　methods　for　the　shear　capability　and　shearing　performance　for　joints　in　reinforced　concrete　frames　subjected　to　bidirectional　loading　have　not　been　reported.　In　this　work,　the　shear　mechanism　of　the　beam-column　joint　in　a　reinforced　concrete　frame　under　bidirectional　loading　is　analyzed.　The　study　shows　that　when　a　synthetic　shear　force　is　imposed　on　the　joint,　the　oblique　compression　zone　comes　into　being　at　the　corner　of　the　joint,　and　the　oblique　compression　strut　is　formed　in　the　core　area　of　the　joint,　which　is　different　from　the　shear　mechanism　of　the　joint　under　unidirectional　loading.　A　shear　capacity　calculation　model　is　established　based　on　the　strut-and-tie　model.　Through　the　testing　of　reinforced　concrete　frame　joints　under　bidirectional　monotonous　loading,　the　combined　shear　and　deformation　in　the　joint　are　obtained,　the　mechanical　properties　in　each　principal　plane　and　in　the　combined　shear　action　plane　are　analyzed,　the　shearing　performance　of　the　joints　in　a　reinforced　concrete　frame　under　bidirectional　loading　is　defined,　and　the　shear　contributions　of　hoop　and　column　reinforcement　are　verified.　The　predicted　values　of　the　shear　capability　in　this　work　are　in　good　agreement　with　the　reported　experimental　results.