Based　on　low-period　cyclic　load　tests　of　compound　damper　with　concealed　X　type　mild　steel　lead　and　mild　steel　damper,　this　paper　carried　out　theoretical　analysis　of　the　compound　damper.　The　theory　hysteretic　curves　of　the　dampers　fit　well　with　tested　hysteretic　curves　of　the　dampers,　and　in　the　paper　a　hysteretic　model　for　the　compound　damper　is　suggested.　The　damper　is　used　in　the　energy　dissipation　system　of　a　suspension　structure.　Then,　the　time　history　analysis　of　earthquake　responses　of　the　energy　dissipation　system　is　carried　out.　The　results　show　that　the　energy　dissipation　system　of　the　compound　damper　with　concealed　X　type　mild　steel　lead　is　of　good　seismic　performances.