Abstract: The effects of two-dimensional disturbance, induced by a circular cylinder placed upstream, on the aerodynamic characteristics of a circular disk have been investigated in wind tunnel. The pressure distribution on the windward surface of the disk was studied with different cylinder diameters and spacing distances. The mechanism of the passive flow control method was discussed combined with previous flow visualization experiments. When the non-dimensional spacing (L/D) between the cylinder and the disk is below 0.7, the low-pressure area on the windward surface of the disk expands rapidly with the spacing increase. While the spacing ratio L/D is greater than 0.7, the low-pressure area keeps in a constant value with the increase of the spacing (the cylinder has the same diameter), and the low-pressure area increases with the cylinder diameter increase. In addition, this disturbance technique can reduce the drag of the disk, and the maximum drag reduction is up to 9% of that of the isolate disk. The corresponding drag of the cylinder-disk system can be reduced by about 4%.