The　arch　dam-foundation　rock　dynamic　interaction　and　the　nonlinear　opening　and　closing　effects　of　contact　joints　on　arch　dam　are　important　to　the　seismic　response　analysis　of　arch　dams.　Up　to　date,　there　is　not　yet　a　reasonable　and　rigorous　procedure　including　the　two　factors　in　seismic　response　analysis.　The　methods　for　the　analysis　of　arch　dam-foundation　rock　dynamic　interaction　in　frequency　domain　are　not　suitable　to　the　problem　with　nonlinear　behaviors,　in　this　paper,　so　an　analysis　method　in　time　domain　is　proposed　by　combining　the　explicit　finite　element　method　and　the　transmitting　boundary,　and　the　dynamic　relaxation　technique　is　adopted　to　obtain　the　initial　static　response　for　dynamic　analysis.　Moreover,　the　influence　of　arch　dam-foundation　dynamic　interaction　with　energy　dispersion　on　seismic　response　of　designed　Xiaowan　arch　dam　in　China　is　studied　by　comparing　the　results　of　the　proposed　method　and　the　conventional　method　with　the　massless　foundation,　and　the　local　material　nonlinear　and　nonhomogeneous　behaviors　of　foundation　rock　are　also　considered.　The　reservoir　water　effect　is　assumed　as　Westergaard　added　mass　model　in　calculation.　The　influence　of　the　closing-opening　effects　of　contact　joints　of　arch　dam　on　the　seismic　response　will　be　studied　in　another　paper.