For a diesel generator, the cooling package is usually composed of radiator and charge air cooler (CAC). The front face of the CAC is usually less than the radiator, and the top of the CAC is equal with the radiator, the assemblage of this kind will not reach the maximum performance of the cooling package. Wind tunnel tests showed that, if the bottom of the CAC was leveled with the radiator, when the cooling air speed was between 1.61～4.66 m/s, the heat exchange ability of radiator would rise by 0%～5.7% and the pressure drop of the cooling package would reduce by 0%～5.5%. At the cooling air speeded of 3.4 m/s, the radiator had the best heat exchange performance. The pressure drop of the cooling package decreased with the wind speed.