Abstract: In response to the unsatisfactory performance of the cooling system in the engine compartment of an off-road vehicle,an analysis based on 3D simulation and supplemented by 1D simulation is made to improve the thermal management of the engine compartment.By means of 3D simulation,the flow field and temperature field of the engine compartment are analyzed,and the high temperature heat damage parts in the engine compartment are pointed out.By means of 1D simulation,the outlet water temperature of the engine and the outlet air temperature of the hot end of the intercooler are obtained,and the corresponding ATD value and intercooler constant are calculated.On suchbasis,an improved scheme of adding a deflector is adopted to improve the intercooling constant.The simulation results show that there is obvious heat recirculation in the area above the intercooler in the engine compartment,which causes the intercooler constant to fail to meet the requirements.After installing the deflector,the air intake of the intercooler has increased.Its return flow has been reduced,and in the meantime,the intercooling constant drops to to 21.31 ℃ from 28 ℃.These research results provide technical support for the research and development of this off-road vehicle and help reduce its R&D cycle.