The invention discloses an electric transmission line unmanned plane relay flying inspection method. An unmanned plane, two remote controllers, a standby battery, two sets of image collection and transmission devices, a transport vehicle and electric transmission line post towers to be inspected are provided. The method is characterized in that operators are divided into two groups, the first group is used for controlling the controllable maximal distance of the unmanned plane flying to the first remote controller; then the second group is used for continuously controlling flying inspection by the unmanned plane through the second remote controller, and controlling the controllable maximal distance of the unmanned plane flying to the second remote controller; then the steps are repeated in sequence. According to the method, in the inspection process, through relay flying, two operators can conduct observation of the unmanned plane and returned images in a ground station in the inspection process simultaneously, so that the safety and inspection quality of the unmanned plane can be ensured; the landing time when the unmanned plane returns after the inspection is finished is saved, fine inspection of the single base post towers is realized, the transition time of the operators is saved, and the work efficiency is improved.