Abstract: In order to further realize the fine inspection of UAV for 500 kV double-circuit transmission lines on the same tower, the minimum safety distance, electromagnetic protection design, trajectory planning of upper and lower lines and patrol lines are studied, and a low-altitude inspection of UAV for transmission lines and its electromagnetic protection measures and trajectory planning methods are proposed. Based on the fact that the UAV is not subject to electromagnetic interference, the safe distance of each phase line inspection is determined. According to the fact that the UAV does not have arc discharge, high image recognition and simulation test, the minimum safe distance of the UAV low-altitude flight is determined. The upper and lower line trajectories of different paths are analyzed to obtain the navigation path with the smallest electric field intensity, and the distance between the patrol lines is maintained by binocular ranging. The designed UAV autonomous inspection system is based on electromagnetic field sensors to monitor the size of the electric field in real time, and corresponding avoidance measures can be taken when the threshold is exceeded. The overall design can ensure the safety, reliability and stability of the UAV in the inspection and navigation of 500 kV double-circuit transmission lines on the same tower, and greatly improve the accuracy and safety performance of the UAV inspection.It provides a reference scheme for the same type of transmission line to realize the fine inspection of UAV.