To　study　the　effect　of　determination　of　damping　matrix　on　the　seismic　response　of　nuclear　power　plant　structures,　fitting　accuracy　of　the　proportional　damping　of　nuclear　power　plant　structures　and　the　influence　of　different　shape　of　structures　were　considered.　On　this　basis,　a　more　precise　model,　that　is,　an　equivalent　proportional　damping　model　was　set　up.　Furthermore,　a　corresponding　method　for　the　seismic　response　analysis　of　nuclear　power　plant　structures　was　proposed　based　on　determining　the　proportional　damping　coefficient　by　weighted　least　square　fitting　method.　The　application　and　analysis　show　that　the　results　by　the　proposed　method　are　closer　to　the　exact　solutions　than　by　the　method　with　traditional　damping　coefficient,　and　it　is　suitable　for　the　seismic　response　of　nuclear　power　plant　structures.　©,　2015,　Chinese　Vibration　Engineering　Society.　All　right　reserved.