Abstract: Based on available analytical and experimental results, a new explanation for the mechanism of the rain-wind-induced vibration was introduced. Meanwhile, a device designed to restrain the larger displacement of a stayed-cable was proposed to mitigate the rain-wind-induced vibration. Analytical and numerical methods were used to simulate the phenomena of the rain-wind-induced and the results were in good accordance with available analytical or experimental ones. Further, the influences of the gap and the location of the device, which may affect the efficiency of the device, were studied. It concluded that the mechanism of the rain-wind-induced vibration could be explained as the action of the centrifugal force of the water around the circumference of the cable’s surface. And the effectiveness of displacement-restriction device on mitigating large-amplitude vibration could be explained by both the theory of energy and the mechanism of rain-wind-induced vibration. With regard to the efficiency of the device, it was found that the smaller the gap between the device and the cable, and the further the location of the device from the end of the cable; that the more significant effect could be achieved to mitigate the vibration of the cable.