The　ground　motion　is　multidimensional,　random　and　uncertain　in　directions　when　earthquakes　occur,　so　dynamic　response　under　oblique　seismic　action　needs　to　be　considered　in　the　structure　design.　A　frame　structure　with　different　stiffness　in　two　horizontal　directions　was　analyzed　under　seismic　action　with　different　input　angles.　The　maximum　response　of　beams　and　columns　was　obtained.　The　seismic　mechanism　of　structures　under　oblique　seismic　action　was　discussed.