Abstract: Vortex-induced vibrations (VIVs) of stay cables frequently occur due to low onset wind velocities, which might cause fatigue failures of stay cables. Thus, it is of great significance to study and design the countermeasures of VIVs of stay cables. Based on the mechanism of VIVs of stay cables, a countermeasure, i.e., O-rings, is proposed to control VIVs of stay cables. VIV responses of standard cables and ring-attached cables are compared by wind tunnel tests. The control effect and influence pattern of the geometrical parameters of O-rings on VIV are investigated. Moreover, the mechanism of suppressing VIVs is preliminarily analysed. The results show that O-rings can effectively suppress VIVs of stay cables. The VIV amplitude can be reduced by 13%~98% for O-rings with different parameters. In general, as the width and thickness increase or the spacing decreases, the control effect on VIVs becomes better. When O-rings are installed, the three-dimensional geometry of stay cables intensifies the three-dimensional flow field. This further leads to the reduction of Karman vortex shedding and VIVs.