The　circulation　pump　is　an　important　element　limiting　the　development　of　small-scale　Organic　Rankine　Cycle　system　which　may　have　a　negative　efficiency　when　the　power　consumption　of　the　pump　is　considered　and　if　a　suitable　pump　that　corresponds　to　the　working　fluid　is　not　properly　selected.　Based　on　the　consideration　mentioned　above,　in　this　paper,　a　trapezoid　used　to　represent　the　power　consumption　of　the　pump　and　a　triangle　used　to　represent　the　degree　of　subcooling　of　the　working　fluid　are　defined.　Using　these　two　models,　the　perfection　of　Organic　Rankine　Cycle　at　the　optimal　condensation　temperature　relative　to　the　Carnot　cycle　within　the　same　temperature　limitation　is　analyzed　when　69　dry　and　isentropic　working　fluids　are　used　in　Organic　Rankine　Cycle.　The　deviation　between　the　real　and　ideal　gas　behavior　of　each　working　fluid　is　also　obtained.　On　this　basis,　the　optimal　condensation　temperature　of　each　dry　and　isentropic　working　fluid　is　determined.　Moreover,　the　applicability　of　each　organic　working　fluid　in　Organic　Rankine　Cycle　is　discussed　from　the　viewpoint　of　pump　performance.　36　working　fluids　are　suitable　and　33　ones　not　suitable　for　the　application　in　small-scale　Organic　Rankine　Cycle　system.　Suitable　pump　types　corresponding　to　applicable　organic　working　fluids　are　also　analyzed　and　determined.　The　graphic　method　proposed　in　this　paper　and　the　findings　about　pump　performance　can　provide　reference　for　the　operation　of　practical　Organic　Rankine　Cycle.