The subject of this paper is the design, analysis and control of a biped line walking robot for inspection of power transmission lines. The novel mechanism enables the centroid of the robot concentrate on the hip joint to minimize the drive torque of the hip joint. The line-walking cycle of the designed mechanism is composed of a single-support phase and a double-support phase. During the process of single-support phase, one foot hangs from the line and the other foot swings from the rear to the front to overcome obstacles on the line and realize line-walking locomotion. The mechanical structure of the robot is discussed, as well as forward and inverse kinematics for motion planning. Dynamic model is established in this paper to analysis the reachable robot workspace in the single supported phase. Finally a PD+ gravity compensation method is introduced for the controller design. The feasibility of this concept is then confirmed by performing experiments with a simulated line environment.