In　current　seismic　design　code　of　each　country　in　the　world,　the　mainstream　of　earthquake　input　for　calculating　the　building　is　to　use　X　and　Y　directions　conveniently.　The　X　and　Y　directions　are　the　main　axis　of　the　building,　and　the　strong-column　weak-beam　damage　mechanism　has　been　considered　only　followed　to　these　main　axis.　However　the　building　response　in　the　oblique　direction　is　higher　than　in　the　main　axis,　and　the　frequency　in　the　oblique　direction　of　the　building　is　higher　than　the　X　or　Y　direction　as　well.　Moreover　the　column　usually　connects　with　two　beams　in　the　orthogonal　directions　and　the　strength　ratio　of　the　column　to　beams　in　the　oblique　direction　is　less　than　in　X　or　Y　direction.　Therefore　it　could　be　the　major　reason　to　cause　the　column-plastic-hinge　damage　mechanism　during　the　earthquake.　In　this　paper,　it　is　discussed　how　the　seismic　input　in　the　oblique　direction　influence　on　the　strong-column　weak-beam　damage　mechanism　for　RC　frame　through　the　perspectives　of　the　dimensional　mechanical　analysis,　cyclic　loading　experiment　and　the　finite　element　analysis　for　the　dimensional　column-beam　joint,　and　then　proposed　that　considering　the　seismic　input　in　the　oblique　direction　is　necessary　in　the　future　structural　design　in　order　to　reach　the　actual　strong-column　weak-beam　mechanism.　©　(2011)　Trans　Tech　Publications.