Aiming at the low-speed climbing condition of a commercial vehicle， a three-dimensional hydrodynamics simulation method is used to study heat management in some commercial vehicle cabins. The mechanism of the heat dissipation influencing the coolant system is focused on. The ventilation rate of the radiator and the outlet temperature of the radiator are taken as the experimental targets. By introducing the orthogonal design and Box-Behnken experiment design method， combined with the establishment and analysis of the regression equation， the relationship between the moving distance of the condenser， the moving distance of the cooling fan， and the extension of the windshield are constructed and optimized. A set of experimental design and optimization processes suitable for engine room thermal management is put forward， which provides a reference for the layout of heat dissipation components in the engine room. The results show that the change in the position of the coolant systems in the commercial vehicle cabin affects the airflow state and temperature field， thus affecting the heat dissipation performance of the engine room. After optimization， the ventilation capacity of the commercial vehicle radiator is improved by 5.26%，the outlet temperature of the radiator is reduced by 3.44%， and the heat dissipation efficiency of the engine room is significantly improved.