The invention discloses a deicing device for a power transmission line. The deicing device comprises a main frame body. The main frame body comprises a first longitudinal beam, a second longitudinal beam and a third longitudinal beam. The first longitudinal beam and the second longitudinal beam are respectively provided with hook units. Each hook unit comprises a first hook assembly and a second hook assembly, wherein the first hook assembly and the second hook assembly can slide back and forth along the first longitudinal beam. The first hook assembly and the second hook assembly are opposite to each other. A power unit is arranged between the first longitudinal beam and the second longitudinal beam, and between the second longitudinal beam and the third longitudinal beam, respectively. The power unit can drive a third roller to walk along the power transmission line. A U-shaped fixing frame is arranged on the second longitudinal beam. A tensioning unit is arranged on the U-shaped fixing frame. The power transmission line can be bent at the fourth roller of the tensioning unit through the tensioning unit. According to the device, the characteristics that the ice is brittle and hard can be utilized. An ice layer on the surface of the power transmission line is broken through the local bending of the power transmission line. Therefore, the insulation layer of the power transmission line is prevented from being damaged.