The invention discloses a resonant wireless power supply system for a high-voltage power transmission line. The resonant wireless power supply system comprises a high-voltage electricity taking device, a high-frequency electric power transmitting device and a high-frequency electric power receiving device, wherein the high-voltage electricity taking device and the high-frequency electric power transmitting device are arranged in a high voltage circuit; the high-frequency electric power receiving device is provided with a rod tower and used for powering an online load monitoring device; a high-frequency inversion unit adopts an MOS pipe as a switch pipe, adopts a single-phase full-bridge inversion circuit and is formed by connecting two bridge arms in parallel, each bridge arm consists of an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm of the same bridge arm cannot be simultaneously switched on; a high-frequency rectification drive unit comprises a rectification bridge, the rectification bridge is uncontrolled full-bridge rectification and consists of four pairs of schottky diode pairs, and the schottky diode pair is formed by connecting two schottky diodes in parallel. The resonant wireless power supply system is simple in structure, convenient to install, capable of directly taking electricity from the high voltage circuit and capable of guaranteeing the normal operation of a circuit monitoring device.