The　organic　Rankine　cycle　(ORC)　system,　which　recovers　the　engine　waste　heat,　can　improve　the　energy　utilization　of　the　engine.　This　paper　analyzed　basic　ORC　and　superheat　ORC　using　R123　as　working　fluid,　respectively.　The　results　show　that　superheating　the　working　fluid　cannot　gain　the　output　power　or　improve　the　system　efficiency　effectively,　while　increase　the　irreversible　loss　of　the　system.　Meanwhile　superheat　ORC　system　induces　that　the　engine　waste　heat　cannot　utilize　fully.　So　superheat　ORC　system　is　not　fit　for　the　engine　waste　heat.　©　2011　IEEE.