Based on the theory of uniform transmission line, an equivalent circuit model and an equivalent distributionparameter circuit model are established respectively for studying the deicing process of transmission lines. The determinizing method for the optimal frequency and voltage of the deicing power supply is then given. A transmission line with the rated voltage of 110 kV is adopted as an example. Combinations of frequency and voltage are obtained at several dielectric loss angles. Finally, the effects from the frequency and voltage on the thermal power and power factor along the transmission line are analyzed by utilizing MATLAB/Simulink. The research results show that both frequency and voltage of the deicing power supply play a decisive role in deicing process of transmission lines. The proposed method can not only realize reliable and efficient deicing effects for icecovered lines, but also reduce the requirements of the deicing power supply on its power electronics selection in terms of switching frequency and withstand voltage level.