The galloping of ice-covered transmission lines is one of the main reasons for line outages. Accurately predicting the outage probability of line galloping and taking corresponding preventive measures is of great significance for improving the safety and stability of power grid operation. In this paper, a novel method to calculate the outage probability of the galloping of ice-covered conductors is proposed. This method firstly establishes the ice-covered conductor galloping equation based on principle of D′Alembert, which takes into account the influence of adjacent gear galloping, and adopts the Runge-Kutta method to obtain the galloping amplitude. The proposed method further improves the accuracy of the dancing model. Secondly, according to the galloping amplitude, the calculation method of galloping trip probability considering the dispersion of air-gap breakdown voltage, and the calculation method of galloping disconnection probability considering the aging effect of transmission lines are proposed, then the outage probability of line galloping is comprehensively obtained. Finally, the example results prove the validity of the model and calculation method proposed in this paper, which can provide certain auxiliary support for the prevention and control of transmission line galloping disasters.