The invention discloses a device for assisting a robot for an overhead transmission line to automatically get on/off a line. The device comprises a pulley mechanism, a hoisting rope and a hoisting gripper mechanism; the pulley mechanism is arranged on an overhead conductor; the hoisting rope is mounted on the pulley mechanism, one end of the hoisting rope is connected with a traction device, and the other end of the hoisting rope is connected with a hoisting ring; one end of the hoisting gripper mechanism is provided with a connecting end for mounting an inspection robot, and the other end of the hoisting gripper mechanism is provided with two grippers which are arranged symmetrically; the opening degree between the two grippers is adjustable; the robot can be separated from or fixed on the hoisting ring through controlling the opening and closing of the grippers; the hoisting gripper mechanism is provided with a self-locking mechanism for ensuring that the grippers are kept in a locked state in a hoisting process. By using the device, the function that an autonomous obstacle-surmounting inspection robot for the overhead transmission line automatically gets on/off the line is achieved; and the device is simple in structure, easy to realize and high in degree of automation and also has other advantages.