Working　fluid　selection　is　crucial　for　organic　Rankine　cycles　(ORC).　In　this　study,　the　relationship　between　molecular　structure　and　ORC　performance　was　established　based　on　the　quantitative　structure-property　relationship　(QSPR)　and　working　fluid　parameterized　model　(WFPM),　from　which　an　ORC　working　fluid　was　actively　designed.　First,　the　QSPR　model　with　four　properties,　namely,　critical　temperature　(T-c),　boiling　point　(T-b),　critical　pressure　(p(c)),　and　isobaric　heat　capacity　(c(p)(0)),　was　built.　Second,　the　evaporation　enthalpy　(h(vap)),　evaporation　entropy　(s(vap)),　and　thermal　efficiency　(eta)　were　estimated　by　WFPM,　and　the　results　were　compared　with　those　using　REFPROP　to　verify　the　calculation　accuracy　of　the　＂QSPR+WFPM＂　coupling　model.　The　average　absolute　relative　deviations　of　evaporation　enthalpy　and　entropy　are　below　8.44%.　The　maximum　relative　error　of　thermal　efficiency　is　6%.　Then,　the　thermodynamic　performance　limit　of　ORC　and　corresponding　thermophysical　properties　of　the　ideal　working　fluid　were　calculated　at　typical　geothermal　source　conditions.　Finally,　the　active　design　of　the　working　fluid　was　conducted　with　the　ideal　working　fluid　T-c　and　p(c)(　)as　the　target.　The　research　shows　that　C3H4F2　and　C4H3F5　are　optimal　working　fluids　at　473.15　and　523.15　K　heat　sources,　respectively.