For the disaster brought by the transmission line regelation, a new de-icing method is presented in this paper. It is supposed that the ice and transmission line are combined closely when there is no external loads, the composite structure of ice-transmission line is set up with the finite element analysis software SAP2000, the 500KV cat-head tower used in the practical projects is applied, then the coupled model of the composite structure-tower is set up. The composite structure can be applied to exciting loads, the frequency of which is close to the natural frequency of ice, the model of which is simulated by the finite element analysis software SAP2000. The natural frequency of ice is far from that of the transmission line. Based on the resonance theory, the ice occurs to deform and crush, finally the ice divorces from the conductors under the function of the exciting load, but those transmission lines are still very safe, the analytical solution can be obtained and the new de-icing method for transmission line based on the theory of resonance is got. It is suitable for the transmission line to de-ice through the computation of the concrete example. It can be concluded that the de-icing method based upon resonance theory is feasible.