Abstract: Under combined actions of both wind and rain, the cables in cable-stayed bridges would vibrate very extensively and strongly. The mechanism of the rain-wind-induced vibrations has received great concerns. The fluid field around a cable with a water-line is simplified into a 2-D flow over the cable section problem to compute the aerodynamic loadings. With these loadings, two simplified vibration models of the cable and the water line, are adopted to study the stability of motions of the cable and the water-line. Computational results show that the rain-wind-induced vibrations are due to the coupling action of vortex-induced vibrations and galloping vibrations of wake.