In order to study the effect of cooling modules position change on air flow and cooling of the engine compartment, such as condenser, intercooler, water tank, radiator and fan, a heavy-duty truck’s complicated geometric model was simplified. In the pre-processing software Hyper-mesh, high-quality grid was generated. Then division of the grid, solving and post-processing of the calculation results was finished using star-ccm+, which is a general heat flow analysis program. Three improving cases were brought out to change the arrangement of the cooling modules in the original truck model. The third case contains five small solutions which is that cooling parts moving along the Z axis is 40 mm, 80 mm and 120 mm, 160 mm and 200 mm. Each of the case was analyzed and the results were compared. According to the results, we are able to find whether the change of the cooling modules has any effect on the flow structure. Furthermore, the temperature distributions under these cases were compared. The cooling air flow which flow through the radiator and the outlet water pipe’s temperature was monitored and the best arrangement of the cooling modules was founded.