Two-stage　Rankine　cycles　draw　more　and　more　attention　with　the　increasing　trade　of　LNG　(liquefied　natural　gas)　and　the　recovery　of　both　the　cold　exergy　of　LNG　and　the　thermal　exergy　of　low　temperature　heat　source.　To　figure　out　the　best　configuration　of　two-stage　Rankine　cycles,　three　mostly　studied　configuration,　cascade　two-stage　ORC　(organic　Rankine　cycle),　parallel　two-stage　ORC　and　two-condensation　ORC　are　optimized　and　compared　under　different　heat　source　temperatures　and　different　NG　distribution　pressures.　Ten　substances　are　selected　as　the　working　fluids.　The　evaporation,　condensation　and　expander　inlet　temperatures　of　both　ORCs　and　the　LNG　regasification　pressure　are　optimized　to　obtain　the　maximum　exergy　efficiency.　The　results　show　that　both　the　increase　of　heat　source　temperature　and　the　decrease　of　NG　distribution　pressure　can　improve　the　exergy　efficiencies　greatly.　The　increase　of　heat　source　temperature　not　only　increases　the　optimal　key　parameters　but　also　affects　the　ranking　of　optimal　fluids,　while　the　increase　of　NG　distribution　pressure　only　affects　the　optimal　parameters.　Different　from　conventional　Rankine　cycles,　there　is　also　an　optimal　condensation　temperature　to　match　the　heat　absorption　line　of　LNG　and　it　increases　with　increase　of　the　NG　distribution　pressure.　The　LNG　regasification　pressure　is　a　key　parameter　which　determines　the　proportion　of　power　outputs　between　ORCs　and　direct　expansion　cycles.　The　thermodynamic　performances　of　parallel　two-stage　ORC　and　two-condensation　ORC　are　almost　the　same,　which　are　obviously　better　than　that　of　cascade　two-stage　ORC.　Both　parallel　two-stage　ORC　and　two-condensation　ORC　with　ammonia　as　the　working　fluid　achieve　the　maximum　efficiency　of　30.54%　under　the　heat　source　temperature　of　200　and　the　NG　distribution　pressure　of　3　MPa.　Two-condensation　ORC　is　the　optimum　configuration　with　both　good　thermodynamic　and　economic　performances.　The　lowest　electricity　production　cost　of　two-condensation　ORC　achieved　in　this　paper　is　0.033$/kW·h.　The　environmental　side　effect　caused　by　working　fluid　leakage　is　negligible　compared　with　the　saved　CO2　emission　via　the　electricity　generation.　©　2020　Elsevier　Ltd