Aiming　at　the　current　researches　of　organic　Rankine　cycle　(ORC)　focusing　on　the　ideal　engine　conditions　but　insufficient　under　real　road　conditions,　an　investigation　for　energy　saving　potential　of　ORC　system　under　real　road　conditions　is　carried　out.　A　vehicle　model　including　the　models　of　engine,　ORC　system,　power　transmission　system　and　the　other　components　is　established　by　different　templates　in　GT-Suite.　Simulations　show　that　the　engine　and　ORC　system　models　are　accurate.　The　vehicle　model　is　used　to　analyse　the　exhaust　energy　characteristics,　and　the　operation　characteristics　and　energy　saving　potential　of　ORC　system　under　the　new　European　driving　cycle　(NEDC)　and　the　heavy-duty　diesel　truck　(HHDDT)　high-speed　cruise　road　conditions.　The　exhaust　energy　fluctuates　greatly　under　NEDC　road　condition,　ranging　from　5.8　kW　to　36　kW,　with　the　average　energy　recovery　efficiency　of　2.01%.　The　average　exhaust　energy　in　urban　road　conditions　is　10.3　kW,　with　the　average　energy　recovery　efficiency　of　1.34%.　The　average　exhaust　energy　in　suburban　road　condition　is　18.3　kW,　with　the　average　energy　recovery　efficiency　of　3.32%.　The　exhaust　energy　fluctuates　slightly　under　HHDDT　high-speed　cruise　condition,　ranging　from　5.2　kW　to　27.7　kW,　with　the　average　exhaust　energy　of　20.0　kW　and　the　average　energy　recovery　efficiency　of　4.01%.　The　ORC　system　is　more　suitable　for　high-speed　cruise　or　suburban　road　condition,　while　for　the　urban　road　condition　with　lower　speed　and　greater　fluctuation,　it　ought　to　be　avoided　as　far　as　possible.　©　2020,　Editorial　Office　of　Journal　of　Xi＇an　Jiaotong　University.　All　right　reserved.