Abstract: Slender cylindrical structures are often subject to vortex-induced-vibrations， which can lead to structural safety problems. The aerodynamic suppression measure with small drag is one of the ideal approaches to solve this issue. To this end， wind tunnel test of the cylinder with a new type of C-ring is carried out in this paper. Influence of the C-ring with different diameters and central angles on the aerodynamic forces of the cylinder under different Reynolds number is comprehensively investigated. Meanwhile， mechanism of the drag reduction and vibration suppression of the C-ring is analyzed and revealed according to wind pressure distri? bution on the cylinder surface. The results indicate that drag of the cylinder in the subcritical Reynolds number range can be effec? tively reduced by weakening negative pressure on the leeward， and the wake vortex shedding can be obviously restrained by inter? ference of the wake.