The embodiment of the invention discloses an optical fiber-based power supply method and device of high-voltage on-line monitoring equipment. The power supply method and device is used for solving the problems of insufficient power supply reliability of the on-line monitoring equipment and some problems in aspects of power supply distance, power supply efficiency and power supply stability and reliability in the prior art are solved. The method disclosed by the embodiment of the invention comprises the steps of acquiring an alternating current on line by an energy taking coil of a high-voltage line; starting control by a laser, and converting first electric energy of the alternating current to light energy; transmitting the light energy to a photoelectric conversion battery through an optical fiber by the laser, and converting the light energy to second electric energy; and outputting the second electric energy converted from the light energy to the on-line monitoring equipment. The optical fiber-based power supply method of the high-voltage on-line monitoring equipment, disclosed by the embodiment of the invention has the advantages that 1, a few restrictions are generated on the power supply distance, and the length of the optical fiber can be determined according to actual distance requirement; and 2, the laser is directional energy flow with high energy density, and the energy attenuation is low and the transmission efficiency is high after through transmission of the optical fiber.