A　regenerative　organic　Rankine　cycle　(RORC)　system　is　designed　to　recover　the　exhaust　heat　of　diesel　engine.　The　organic　working　fluids　under　investigation　are　the　pure　fluid　R245fa　and　the　zeotropic　mixture　Mix　(isopentane　and　R245fa　mixed　in　7/3　mole　fraction).　The　influence　of　intermediate　pressure　(pressures　at　which　the　steam　is　extracted　from　the　expander)　on　the　performance　parameters　of　the　RORC　system,　such　as　the　net　power　output,　the　thermal　efficiency,　and　the　mass　flow　rate　of　the　working　fluid,　are　analyzed,　and　on　the　basis　of　the　analysis　results,　the　intermediate　pressure　is　set　to　1.15　MPa　for　the　RORC　system　using　Mix　and　1.2　MPa　for　the　RORC　system　using　R245fa.　Then　the　performance　of　the　RORC　system　using　the　two　different　working　fluids　is　analyzed　over　the　whole　operating　range　of　the　diesel　engine,　respectively.　The　calculation　results　show　that　Mix　is　the　better　selection　for　the　RORC　system　than　R245fa.