When a car was testing on its entire vehicle cooling temperature field, it was found that the temperature of its engine compartment air inlet, radiator fan surface, speed sensor, battery surface and other parts exceeded its temperature value of the design of thermal limit. Through computer simulation, by using fluid analysis software Fluent to conduct thermal flow field simulation analysis of engine compartment, this paper found that the interior recirculation of engine cabin was serious. Through optimizing analysis, by increasing foam cushion block, and by blocking front grille cover, the interior recirculation phenomena in the engine cabin were effectively controlled.