Abstract Organic Rankine cycle (ORC) system has been widely used in waste heat recovery (WHR) from exhaust gas of internal combustion engine (ICE) to improve efficiency. Due to the real road condition, the heat source of ORC system is always fluctuant and volatile for WHR in automotive internal combustion engine (A-ICE). Thus, two types of ORC system are analyzed to explore the dynamic performance in this paper based on the dynamic models programmed in Dymola. The dynamic behavior is analyzed when ICE operating condition changes and when the changed operating condition gets back to the original state after a period of time. The results show that with fluctuant heat source, the Oil storage/Organic Rankine Cycle (OS/ORC) system has a stronger resistance to the change of operating conditions as well as a better heat recovery performance, and the rate of decline of system power output is lower; but it's apt to occur low temperature corrosion. In addition, with consideration of PID control strategy, evaporation pressure drops 1.43 bar and 2.57 bar for the ORC and OS/ORC system rather than 8.69 bar and 11.54 bar, and the degree of superheat can be prevented from declining to zero, ensuring a safety operation of system.