Engine cooling system of construction vehicle usually consists of cooling fans and radiators. Based on the entropy and exergy efficiency evaluation parameters of radiator, cooling fan was introduced as an element of evaluation objects to realize the evaluation of cooling system. The method was applied to topdown design of domestic doubledun vibration road roller, which made optimization and selection of cooling fan come true. The results show that the cooling system can be evaluated by considering the cooling fan and radiator together and using the air volume flow rate as public variable. According to 3D simulated results, the heat flow temperature error of intercooler, coolant radiator and hydraulic oil is 3.15%, 4.07% and 2.83% respectively. The acquired actual air volume flow rate plays an important role in the whole performance evaluation and product design. Accordingly, the method can be used for cooling fan selection optimization during the topdown design.