Submarine　pipelines　are　vital　lifeline　engineering　structures　for　transporting　offshore　oil　and　gas　resources,　which　may　experience　adverse　vibrations　against　structural　safe　operation　when　encountering　strong　offshore　earthquakes.　This　paper　proposes　an　innovative　casing-pipe　type　tuned　mass　damper　(CPTMD)　for　the　seismic　control　of　free-spanning　submarine　pipelines　(FSSPs).　The　design　concept　and　control　mechanism　of　the　CPTMD　are　firstly　presented.　Both　shaking　table　tests　and　numerical　simulations　are　performed　to　examine　the　effectiveness　of　using　the　CPTMD　to　reduce　seismic-induced　vibration　of　FSSPs,　through　comparing　structural　seismic　responses　with　and　without　damper　device.　In　the　experimental　and　numerical　studies,　the　effect　of　seawater　around　submarine　pipelines　is　simplified　using　the　added　hydrodynamic　mass　method.　The　experimental　and　numerical　results　consistently　demonstrate　that　the　proposed　CPTMD　has　a　good　capacity　for　suppressing　seismic-induced　vibration　of　FSSPs.　Moreover,　the　impacts　of　stiffness,　damping　coefficient,　mass　ratio　and　casing-pipe　length　on　the　seismic　control　effectiveness　of　the　CPTMD　device　are　investigated　and　discussed　comprehensively,　and　the　optimal　values　of　these　design　parameters　are　determined.　As　a　result,　the　proposed　CPTMD　could　be　an　effective　and　simple　solution　for　the　vibration　control　of　FSSPs　induced　by　offshore　seismic　motions.