This project presents a solution to prune trees near the power lines using a robotic system. As trees provide many ecosystem services, they are essential elements to construct the green space. But, some problems are created when they are placed right-of-way the power lines. This causes that tree branches have more growth toward power lines and then, they contact with power towers. This contact is one of the major reasons which interrupt power transmission services. In addition, this contact can cause that trees catch fire. To avoid this contact, branches need to be pruned. To control the growth of trees branches along the power lines, the pruning task must be regularly done. This task along the power lines is too dangerous and so, the usage of safe instrument is the first prerequisite. To this end, an autonomous robotic system can be considered. Using this system, the accuracy and quickness of operation is also obtained. Thus, in this project, a robotic system is proposed to prune trees along power lines. This robot is an Unmanned Aerial Vehicle (UAV) which manipulates a swing chain saw system. The assumed flying robot is an Octorotor which was manufactured in AGRINS laboratory of Tehran University.