The　prefered　strong-column　weak-beam　mechanism　had　not　been　realized　in　Wen-Chun　earthquake　and　many　buildings　have　been　damaged　for　the　reason　of　it.　In　this　paper　the　damage　mechanism　of　the　spatial　joint　under　the　45-degree　direction　earthquake　affection　was　discussed　through　the　mechanical　analysis,　cyclic　loading　experiment　and　the　finite　element　analysis.　The　aseismic　design　method　prefered　in　the　code　have　not　considered　the　45-degree　direction　earthquake　affection　and　it　is　considered　as　one　of　the　main　reason　that　the　strong-column　weak-beam　mechanism　had　not　been　realized　in　earthquake,　the　necessity　of　the　45-degree　direction　aseismic　designing　is　also　suggested.