This　study　analyzed　the　variation　law　of　engine　exhaust　energy　under　various　operating　conditions　to　improve　the　thermal　efficiency　and　fuel　economy　of　diesel　engines.　An　organic　Rankine　cycle　(ORC)　waste　heat　recovery　system　with　internal　heat　exchanger　(IHE)　was　designed　to　recover　waste　heat　from　the　diesel　engine　exhaust.　The　zeotropic　mixture　R416A　was　used　as　the　working　fluid　for　the　ORC.　Three　evaluation　indexes　were　presented　as　follows:　waste　heat　recovery　efficiency　(WHRE),　engine　thermal　efficiency　increasing　ratio　(ETEIR),　and　output　energy　density　of　working　fluid　(OEDWF).　In　terms　of　various　operating　conditions　of　the　diesel　engine,　this　study　investigated　the　variation　tendencies　of　the　running　performances　of　the　ORC　waste　heat　recovery　system　and　the　effects　of　the　degree　of　superheat　on　the　running　performance　of　the　ORC　waste　heat　recovery　system　through　theoretical　calculations.　The　research　findings　showed　that　the　net　power　output,　WHRE,　and　ETEIR　of　the　ORC　waste　heat　recovery　system　reach　their　maxima　when　the　degree　of　superheat　is　40　K,　engine　speed　is　2200　r/min,　and　engine　torque　is　1200　N.m.　OEDWF　gradually　increases　with　the　increase　in　the　degree　of　superheat,　which　indicates　that　the　required　mass　flow　rate　of　R416A　decreases　for　a　certain　net　power　output,　thereby　significantly　decreasing　the　risk　of　environmental　pollution.