The invention discloses an insulator flashover fault localization method and system. The method comprises steps of: firstly acquiring an aerial photo of a power transmission line; determining a colorcharacteristic image of a target region according to the aerial photo; determining a structural characteristic image of the target region according to the aerial photo; fusing the color characteristicimage and the structural characteristic image to determine a fused image of the target region; preprocessing the fused image to determine a connected domain; then subjecting the aerial photo to tiltcorrection to determine the tilt correction image of the target region; in the tilt correction image, extracting an image of the insulator region according to the connected domain; determining a flashover region smooth image according to the image of the insulator region; and finally extracting the edge contour of the flashover region smooth image, and drawing in the tilt correction image according to the extracted edge contour to locate a fault and improve the localization accuracy.