In　the　present　study,　the　thermodynamic　and　economic　performance　of　a　combined　thermodynamic　cycle　formed　by　an　ORC　and　a　Kalina　cycle,　which　can　simultaneously　recover　waste　heat　of　exhaust　gas　and　cooling　water　of　marine　engine,　has　been　analyzed.　Two　typical　marine　engines　are　selected　to　be　the　waste　heat　source.　Six　economic　indicators　are　used　to　analyze　the　economic　performance　of　this　combined　thermodynamic　cycle　system　with　different　marine　engine　load　and　under　practical　comprehensive　operating　condition　of　marine　engine.　The　results　of　the　present　study　show　that　the　combined　thermodynamic　cycle　system　with　R123　as　organic　working　fluid　has　the　best　performance.　The　system　with　cis-butene　has　the　worst　economic　performance.　Under　practical　comprehensive　operating　conditions　of　ships,　R123　has　the　shortest　Payback　Periods,　which　are　8.51　years　and　8.14　years　for　8S70ME-C10.5　engine　and　5G95ME-C10.5　engine,　respectively.　Correspondingly,　payback　Periods　of　Cyclopentane　are　11.95　years　and　11.90　years.　The　above　values　are　much　shorter　than　25　years　which　are　the　lifetime　of　a　marine　ship.　Under　practical　comprehensive　operating　conditions　of　ships,　the　combined　cycle　system　can　provide　output　power　which　is　at　least　equivalent　to　25%　of　engine　power.　Considering　that　R123　will　be　phased　out　in　near　future,　cyclopentane　may　be　its　good　successor.　Cyclopentane　can　be　used　safely　by　correct　handling　and　installing　according　to　manufacturer＇s　instructions.