Condensation　temperature　is　one　of　the　crucial　parameters　determining　the　performance　of　an　organic　Rankine　cycle.　It　is　necessary　to　consider　the　differences　in　the　working　fluids　themselves　when　setting　the　condensation　temperature　of　organic　Rankine　cycle.　In　current　study,　temperature-entropy　(T-s)　diagram　is　employed　to　describe　the　difference　in　working　fluids.　Three　areas　of　dry　and　isentropic　fluids　in　a　temperature-entropy　(T-s)　diagram,　which　are　the　area　denoting　net　output　work　of　cycle　(A(1),　the　area　denoting　net　output　work　of　the　Carnot　cycle　(A),　and　the　curved　triangle　in　superheated　region　denoting　condensation　characteristics　(A(2)),　are　defined.　On　this　basis,　the　ratio　of　A(2)　to　A(1)　and　the　ratio　of　A(1)　to　A　are　calculated.　Logarithmic　Mean　Difference　of　the　above　two　ratios　is　obtained　to　determine　the　operable　ideal　condensation　temperature　of　66　dry　and　isentropic　fluids　employed　in　Organic　Rankine　Cycle.　The　findings　indicate　that　the　operable　ideal　condensation　temperatures　for　the　majority　of　dry　and　isentropic　fluids　are　in　the　range　of　305　K　to　310　K.　The　work　presented　in　this　study　may　be　useful　for　designing　and　establishing　an　Organic　Rankine　Cycle　system.