Fluid　selection　and　multi-parameter　optimization　of　two-stage　organic　Rankine　cycle　driven　by　low　grade　heat　source　and　liquefied　natural　gas　were　studied.　Under　the　combination　of　400　kinds　of　working　fluids,　the　multi-parameter　optimization　of　evaporation　temperatures,　condensation　temperature,　inlet　temperature　of　expander　of　both　cycle　I　and　cycle　II,　and　evaporation　pressure　of　cold　source　etc.　seven　parameters　were　carried　out.　The　results　show　that　the　critical　temperatures　of　both　suitable　fluid1　and　fluid　2　are　about　50　lower　than　the　heat　source　temperature.　When　the　critical　temperature　is　within　the　optimal　range,　for　cycle　I　working　substance,　the　triple　phase　point　and　normal　boiling　point　temperatures　are　as　low　as　possible,　while　for　cycle　II　working　substance,　the　triple　phase　point　temperature　and　the　saturated　temperature　corresponding　to　minimum　allowable　negative　pressure　should　be　lower　than　-50.　The　exergy　efficiency　is　the　largest　when　cycle　I　using　superheat　vapor　and　cycle　II　using　saturated　vapor.　The　condensation　temperature　of　cycle　I　is　lower,　is　better,　while　for　cycle　II,　the　optimal　condensation　temperature　corresponding　to　different　cycle　I　working　substance　has　larger　difference.　©　2017,　Editorial　Board　of　Acta　Energiae　Solaris　Sinica.　All　right　reserved.