In order to explore the mechanism of rain-wind-induced vibration of cables, a modified model for rain-wind-induced vibration of cables was proposed based on aerodynamic coefficients tested by a spatial model with three-dimensional ambient flows. Furthermore, the feasibility of the modified model was verified through a comparison between analytical results and the ones obtained by wind tunnel tests. The characteristics of rain-wind-induced vibration were explored from the aspect of vibration energy. The research indicates that the rain-wind-induced vibration of cables is a type of galloping with a limited amplitude induced by negative slopes of aerodynamic lift coefficients and has the properties of self-excitation and limited amplitude vibrations.