With a fuel cell vehicle as the research object, a combined simulation platform of GT-COOL and STAR-CCM+ has thus been established. One-dimensional and three-dimensional models are combined together to calculate the temperature characteristics in the engine compartment with a volume fraction of 50% ethylene glycol 17 under 100 km/h, 120 km/h, 150 km/h working conditions respectively. The calculation results show that the installation of the deflector can effectively improve the air flow rate, and reduce the temperature of the cooling medium at the outlet of the main radiator and the left and right radiators, thus achieving the purpose of improving the heat dissipation performance of the radiator.