The invention provides a high-voltage high-power biharmonic electrical deicing method for an overhead power transmission line. In the method, a high-voltage high-power power electronic variable frequency resonance device outputs two high-frequency voltages with two different frequencies to ensure that two high-frequency currents with two different frequencies can be generated in a resonance capacitor which is connected in series with a transmission line and an LC resonance circuit which is connected in parallel with the transmission line so as to heat an iced transmission line. The two high-frequency currents with two different frequencies are introduced into the iced transmission line, so that the skin effect of the transmission line can be greatly improved, corresponding line equivalent resistance is increased, the ice-melting current of the line is reduced under the condition that the same ice-melting power is generated, and damage of line overcurrent is reduced. The method has the advantages of furthest utilizing capacity of the high-voltage high-power power electronic variable frequency resonance device, along with high ice-melting efficiency and high deicing speed, is applicable to ice-melting of single-phase and three-phase transmission lines, has high actionability and wide application prospect, and can generate enormous economic and social benefits.