The　application　of　the　first　three　generations　of　organic　refrigerants,　namely,　CFCs,　HCFCs,　and　HFCs,　in　an　organic　Rankine　cycle　has　been　widely　investigated.　As　environmentally　friendly　successors　to　the　above　three　generations　of　refrigerants,　hydrofluoroolefins　(HFOs)　and　hydrochlorofluoroolefins　(HCFOs)　have　also　attracted　increasing　research　interest　for　their　application　in　the　organic　Rankine　cycle　(ORC).　Based　on　molecular　complexity,　characteristic　points　on　saturation　liquid　and　vapor　curve　and　area　of　characteristic　regions　in　temperature-entropy　(T-s)　diagram,　eight　common　hydrofluoroolefins　(HFOs)　and　hydrochlorofluoroolefins　(HCFOs)　are　classified,　analyzed,　and　evaluated.　In　addition,　the　type　of　heat　source　and　specific　operating　conditions　in　which　these　eight　hydrofluoroolefins　(HFOs)　and　hydrochlorofluoroolefins　(HCFOs)　are　most　effective　are　recommended.　The　results　show　that　molecular　complexity　of　hydrofluoroolefins　(HFOs)　and　hydrochlorofluoroolefins　(HCFOs)　mainly　depends　on　the　length　of　the　C　chain,　and　then　on　the　number　and　location　of　Cl　and　F　atoms.　HFO-1243zf　has　the　best　comprehensive　evaluation　indicator,　and　it　is　noteworthy　as　a　recommended　working　fluid　for　subcritical　ORC　systems.　The　result　obtained　in　this　paper　may　provide　a　reference　for　the　design　and　actual　operation　of　Organic　Rankine　Cycle　system　using　HFO　and　HCFO　as　working　fluids.　©　2024　Elsevier　Ltd