Compared with the fuel cars, the hybrid cars has higher thermal load of engine room and has higher requirements for heat dissipation performance of the cooling module. Under idling condition, a hybrid car has an actual problem that higher temperature of engine room and inlet air temperature of cooling module. In this paper, a mathematic model of car thermal management is established, numerical simulations on flow and temperature fields of car were performed by using STAR-CCM+ software, the feasibility of the simulation results was verified by the thermal balance test of the cars. The results show that the reflow of hot air and the inlet air temperature of the cooling module are reduced by sealing the cooling module, the front end module and optimizing the structure of deflector, thus, the heat dissipation efficiency of the cooling module is improved.