A regenerative organic Rankine cycle （ORC） system was designed to recover and utilize the waste heat energy from engine exhaust gas efficiently. The mathematical model of regenerative ORC was built up in Matlab and the influences of the factors such as suction pressure, evaporating pressure and expander inlet temperature on system performance were analyzed. Then the regenerative ORC was compared with the basic ORC by using a combined first and second law analysis. According to the results, when the evaporating pressure remained constant, the regenerative ORC system thermal efficiency and exergy efficiency would increase at first, then decrease with the increasing of suction pressure. The mass flow rate increased while the heat transfer rate in the evaporator decreased first and then increased with the increasing of suction pressure. By comparing the two configurations, it was seen that regenerative ORC produced higher efficiency with a lower irreversibility and could recover waste heat energy more effectively.