In this paper, the differences in the characteris-tics of airflow around the van-body truck and of the aerodynamic drag, which were caused by the installation of a wind deflector, were studied by experimentally and numerically. The results show that after the installation of the deflector, the airflow around the top and bottom of the truck becoms smooth, the in-tensity of tail-vortex is weakened and its contribution area less-ened. It also indicates that the aerodynamic characteristics of the airflow are changed distinctly and the aerodynamic drag is re-duced considerably. The effect of the thin-wall deflector is better than the solid one in decreasing the drag. It is also concluded that proper design of the gap between the deflector bottom and the top of the driver cab can enhance the effect of the deflector in reduc-ing drag.