A method for flight path planning of unmanned aerial vehicles using flying routes of birds includes: recording multiple pieces of flight data, wherein multiple recording devices are used to record the multiple pieces of flight data when the birds fly from a first designated point to a second designated point and are respectively installed on the birds; generating an optimal flight path, wherein an analyzing device collects the multiple pieces of flight data and calculates the optimal flight path; and controlling a UAV to fly according to the optimal flight path, wherein the optimal flight path is inputted to the UAV. By virtue of bird's nature automatically avoiding obstruction and adapting to wind direction and air flow, multiple obstruction-free recording points between two places can be acquired to form an optimal flight path with the shortest flying time or distance.