The invention relates to the field of power taking of a power transmission line, in particular to a power transmission line step voltage-based device for acquiring electric energy and an application method of the device. The power transmission line step voltage-based device for acquiring electric energy comprises rear-end equipment, front-end equipment and a high-conductivity insulation wire, wherein a central control module is used for controlling a first roller and a second roller to drive and proceed so as to achieve an inspection proceeding task of power transmission line inspection equipment and controlling a voltage between a step voltage acquisition end A and a step voltage acquisition end B, power is supplied by a storage battery when the device for acquiring the electric energy is in an initial state or other non-working states, the voltage between the step voltage acquisition end A and the step voltage acquisition end B is raised to obtain an appropriate voltage by coordinated voltage of the central control module and a high-gain boost module, the electric energy is normally provided for the power transmission line inspection equipment, the battery is not needed to be replaced during the inspection process, so that the problems of small inspection radius and short endurance time are solved.