The invention discloses a mist spray anti-drifting device for an agricultural unmanned aerial vehicle and a method for applying the mist spray anti-drifting device.The mist spray anti-drifting device comprises a control end, three driving devices and a support rod assembly.The control end comprises a transmitter and a receiver, the driving devices comprise power devices, transmission gears and bases, the support rod assembly comprises a main support rod, a left support rod and a right support rod, and the three driving devices are respectively arranged between the main support rod and an unmanned aerial vehicle body, between the main support rod and the left support rod and between the main support rod and the right support rod and can drive the support rod assembly to be folded and unfolded under the control of the control end; pesticide delivery hoses are arranged in the various support rods of the support rod assembly, and mist spray nozzles are arranged at corresponding positions of the left support rod and the right support rod.The mist spray anti-drifting device and the method have the advantages that the designed support rods are of unfolding and folding structures, can be folded when operation is not carried out and can be unfolded when spray and application operation is carried out; the nozzles are lowered, so that sprayed and applied fog drop can be kept away from influence of wind fields, accurate aviation spray and application operation can be carried out, and the mist spray anti-drifting device is simple in structure and easy and convenient to operate and is small and safe.