The invention discloses a device and a method for taking energy at a high potential end of a transmission line, belonging to the cross technical field of high voltage technology and power supply technology. The device of the invention comprises a capacitor voltage divider, a rectifying module, a DC/DC voltage regulating module, an overvoltage suppressing module and a power supply housing. The invention solves the problem of providing stable and reliable direct current power supply for various on-line monitoring devices located at the high potential end of the transmission line and the main equipment of the substation, The utility model improves the output power of the power supply, provides a flexible and convenient regulation mode for outputting a variety of commonly used DC voltage values, ensures that the insulation requirements of the corresponding transmission line voltage grades are met, has good electromagnetic interference resistance and reduces the cost of the transmission line energy taking device.