Aiming at the practice of intelligent robot inspection of transmission lines, four key control technologies of the robot’s automatic inspection operations are developed including automatically passing over obstacles, automatically positioning, automatic fault diagnosis and restoration, automatic inspection The principle and implementation method of the control technology are introduced in detail. Three typical failure modes of the robot, i.e., the self recovery fault, the replacement fault and the fault need to repair, and their diagnosis and repair strategies are established. The robot inspection test on real outdoor line is carried out. Robot inspection demonstration application of 500 kV live line in China Southern Power Grid is completed for the first time. The robot inspection control technology, fault diagnosis and repair strategy, as well as the independent inspection process are verifid and assessed. The robot has a single time inspection mileage of over 10 km, and the inspection application has achieved good results.