Under the rainy weather, rain-induced vibration on high-voltage (HV) transmission line often occurs, which intensifies fatigue conductors and tower callapses. Mechanism and control measures of the rain-induced vibration have aroused wide attention in power engineering. The mechanism can be explained that the droplets suspended to the conductors amplify corona discharges with ionic wind, forms non-circular cross-sections, and the rain-induced vibration is due to the coupling action of vortex-induced vibration by ionic wind and galloping vibration by external wind force. Based on the mechanism, a valid model on the rain-induced vibration on high-voltage transmission line is proposed based on the finite element theory and the Newmark algorithm. Taking the conductor LGJ-240 as an instance, we investigate the effects of ionic wind and non-circular cross-sections with different parameters on amplitude of the conductors. The result shows non-circular cross-sections have obviously effects, and the ionic wind have a certain influence and easily to coupling with wind force. Mechanism and conclusions in this paper can be used as references to construct High-voltage transmission lines, upgrade the existing lines and control vibration.