The invention discloses an insulator arc-over fault positioning device and a positioning method based on discharging light detection. The insulator arc-over fault positioning device comprises a micro-consumption pinhole camera, a solar battery, a storage battery, an image processing singlechip, a counting unit, a wireless transmission module, an image receiving unit and an alarm unit, wherein the micro-consumption pinhole camera is used for collecting insulator arc-over discharging light, the image processing singlechip is used for controlling the micro-consumption pinhole camera to collect parameters and analyze and judge whether arc-over discharging is incurred to an insulator according to a collecting result, the counting unit is used for counting the number of arc-over times, the wireless transmission module is used for transmitting an arc-over picture to the image receiving unit, the solar battery and the storage battery are used as power supply devices, the image receiving unit is used for receiving and storing the arc-over picture transmitted by the wireless transmission module and the alarm unit is used for transmitting an alarm signal. The insulator arc-over fault positioning device and the positioning method based on the discharging light detection have the advantages of intuitively and effectively positioning the insulator with arc-over fault, improving working efficiency of line walking personnel and shortening fault eliminating time.