Mission planning is an important step in the powerline inspection flying robots. To deal with the tasks of powerline flying robots, a flying robot mission-planning system is established based on the unmanned mini-helicopter model described in this paper. It can determine the best checking order, the optimal space path and the best flight trajectory. The objective function and the constraints are described by establishing the mathematical model, and the mission-planning system is decomposed by using the tiered methods. Multi-agent technology is chosen to solve the mission-planning issue. Finally, simulation is conducted to verify that the mission-planning system is feasible and efficient.