We develop two cooperative robots for power transmission lines (PTLs) inspection – a light climbing robot (CBR) which can stably move on the overhead ground wire (OGW) for sensor data collection and an unmanned aerial vehicle (UAV) with a grabbing mechanism, which can automatically put the CBR on the OGW and take it off. In order to guarantee the safety, the mechanical structures of the connectors are designed in the shape of a trumpet. Further, a self-locked structure of the CBR is developed to automatically seize and release the OGW. For autonomous navigation, the UAV is equipped with a movable sliding rail and a 2D Laser Range Finder (LRF). The LRF can not only detect the position and orientation of the OGW but also detect the top beam of the CBR and the grabbing position in it. Furthermore, the action of the grabbing mechanism is automatically triggered by a microswitch. Finally, by the developed UAV and CBR platforms, we test the whole loading and unloading strategy in an artificially constructed PTLs environment outdoors and achieve an encouraging result. Combining the flexible motion of the UAV and the high inspection accuracy of the CBR, the CBR can negotiate any obstacle by flying and abandon the traditional heavy obstacle crossing mechanism to effectively realize close-proximity inspection. Due to the light weight and low power consumption, the CBRs can be deployed once in many power corridors to conduct a long-term inspection.