Centralized power unit has merits of integrating more variety of power units with higher power, but shortages like complex duct structure, diverse radiator type, and the difficulty of checking the working point of the cooling fan, therefore, the accuracy and efficiency of theoretical calculation could not be assured by using traditional methods. To solve problems mentioned above, the finite element simulation method was introduced. In this method, to find out accurate working points of fan, the model of cooling fan’s duct structure was simplified firstly, which provided an easy path to PQ curve and fan curve of the whole system together. The processing of calculation and results attained by using finite element simulation were presented. Finally, the calculation and simulation method mentioned in this paper was verified by implementing experiment, and the results showed that the reliability and feasibility of this new method were significantly proved. It turned out that the finite element method was a more advanced way on improving calculation precision and efficiency by comparing with the traditional calculation method.