In　seismic　response　analysis　of　high　dam,　the　incidence　of　plane　seismic　waves　is　usually　considered　as　vertical.　To　improve　this　assumption,　an　input　method　of　oblique　plane　seismic　waves　for　threedimensional　calculation　is　proposed　in　the　frame　of　time-domain　wave　method　that　couples　explicit　finiteelement　method　with　viscous-spring　artificial　boundary　condition.　The　new　method　was　applied　to　the　Xiaowan　arch　dam,　and　the　effect　of　incidence　angle　was　examined.　The　results　show　that　in　comparison　with　vertical　incidence,　oblique　incidence　of　seismic　waves　may　cause　significant　increases　in　the　amplitude　amplification　factors　of　displacement,　velocity　and　acceleration　at　key　locations　of　the　arch　dam.　Thus　this　study　suggests　that　oblique　incidence　should　be　accounted　in　the　response　analysis.　©　Copyright.