The invention relates to a high-voltage side mutual inductance energy-acquiring device of a high-voltage power transmission line, comprising an energy-acquiring unit, an impact protective circuit, a filtering and rectifying circuit, a control unit circuit, a charging management circuit and a voltage-stabilizing circuit. By adopting a feedthrough strip coil with a certain turn number, enough energy can be acquired under the condition of low current, and the conversion and the balance of energy can be realized through a high-speed control unit consisting of a comparator, an MOS (Metal Oxide Semiconductor) tube and a high-power resistor under the condition of heavy current, thereby providing a safe, stable and high-precision direct current power supply for power transmission line motoring under the condition of power transmission current in a wide range.