The invention provides a mobile DC power ice-melting method and a device thereof. The method and the device are characterized in that ice-melting treatment is carried out to line icing through a set of movable DC power supply; the movable DC power supply bears a generating set and a controllable rectification system through two motor vehicles respectively; and power is generated through the generating set, rectified through the controllable rectification system and then supplied to lines as DC ice-melting power; the controllable rectification system is provided with a harmonic reactive compensation system; the DC power supply is subjected to harmonic treatment through the harmonic reactive compensation system and then provides the DC power; a controllable rectifier changes the power supplied by the generating set or a substation into the DC power and then supplies the DC power to input lines; the harmonic reactive compensation system sends synchronizing signals into a rectifier control system; and the rectifier control system carries out rectifying harmonic treatment to the controllable rectifier.