Abstract: In the process of obstacle navigation,the inspection robot arm needs to grasp the power line exactly.According to the geometrical characteristics of the transmission line and the theory of perspective projection,a stereo vision method based on single camera is presented to detect the orientation and position vector of the power transmission line.Based on the presented localization algorithm and visual servoing theory,a servo model for line grasping is built up.Visual servo line-grasping experiments have been made with our self-developed inspection robot,and the results verify the validity of the proposed method.