Four types of different flow inlet models were tested to improve the flow uniformity at the inlet of the radiator and to prevent thermal damages of auxiliary units from the hot air in the bus engine room. Measurements and numerical calculations were performed and their results were in a good agreement with each other. Simultaneously temperature measurements were carried out under the conditions of actual bus driving. As designing the new flow inlet at the partition board which seperates the engine space and radiator space, flow circulation can be achieved and fresh air comes into the engine room from the bottom. It was proved that new inlet makes the one air temperature cooling down in the engine room, the other uniformity improvement.