Abstract: To take full advantage of the waste heat from a diesel engine,a set of dual loop organic Rankine cycle( ORC) system was designed to recover exhaust energy,waste heat from the coolant system,and released heat from turbocharged air in the intercooler of a six-cylinder diesel engine. Aspen plus software was used to model the dual loop ORC system. According to the simulation model,the operating performance of the dual loop ORC system and the fuel economy of the diesel engine were investigated. The results show that the thermodynamic performance and economy performance of the diesel engine can be effectively improved by using the dual loop ORC system. Under the certain engine operating conditions,namely,engine speed is 2 000 r / min and engine torque is 1 313 N·m,the total net power output of the dual loop ORC system is up to 43. 65 k W. The brake specific fuel consumption( BSFC) and the thermal efficiency of the diesel engine-dual loop ORC combined system are 191. 24 g /( k W·h) and 37. 57%,respectively. Compared with the diesel engine,the thermal efficiency of the combined system can be increased by 13. 69% and the BSFC can be reduced by 15. 86%.