An　organic　rankine　cycle　(ORC)　system　was　designed　to　recover　waste　heat　from　a　vehicle　diesel　engine　using　pure　fluid　R245fa　and　zeotropic　mixture　R416A　as　working　medium.　Taking　power　output　increasing　rate　as　measure　to　evaluate　the　diesel-ORC　combined　cycle　system,　the　effects　of　the　combined　cycle　system　were　analyzed　under　various　engine　conditions.　Results　show　that　with　engine　speed　and　torque　increasing,　net　power　outputs　of　the　combined　cycle　system　using　both　two　different　working　mediums　increase;　the　max.　net　power　output　increments　are　30.39　kW　for　R416A　and　28.03　kW　for　R245fa.　Combined　cycle　system　power　output　increasing　rates　using　two　working　fluids,　R416A　and　R245fa　reach　up　to　9.70%　and　9.00%　respectively.　The　effect　is　better　when　using　zeotropic　mixture　R416A.