A reconnaissance UAV and a surveillance flight method of the reconnaissance UAV which can reduce a number of required reconnaissance UAVs are provided. The surveillance flight method for detecting an unauthorized UAV includes: defining multiple flight passages in a UAV no-fly zone for a plurality of reconnaissance UAVs; controlling each of the plurality of reconnaissance UAVs to fly across adjacent flight passages at an interval by crossing a border of the adjacent flight passages; and controlling at least one of an image sensor and a noise sensor mounted on the reconnaissance UAV to dynamically change a direction detection thereof.