The invention discloses a device and a method for obtaining energy from a high voltage transmission line, and belongs to the technical field of high voltage technologies and power source technologies.The device comprises a high-voltage capacitor, a first-stage step-down transformer, a bidirectional thyristor module, a rectifier module, a filter capacitor, a voltage monitoring module, a thyristordrive module, a DC/DC voltage regulator module, an overvoltage suppression module and a shielding box. The principle of capacitance voltage division is employed, the high-voltage capacitor set is connected in series with the primary side of the transformer to effectively improve the output power of the device for obtaining energy, two-stage voltage reduction is employed to reduce the insulation design requirement of the transformer and reduce the size of the transformer. The wiring mode is flexibly configured between the high-voltage capacitor and the first-stage step-down transformer to achieve energy obtaining at a high level end between a phase and a ground and a low level end between the phase and the ground and between phase and phase, and the device and the method for obtaining energy from the high voltage transmission line can supply power for various electric devices.