The invention provides an unmanned aerial vehicle drowning rescue device and a method thereof. The unmanned aerial vehicle drowning rescue device includes an unmanned aerial vehicle. The unmanned aerial vehicle includes a vehicle body, a plurality of rotors, a landing gear and a drowning rescue device body. The vehicle body is arranged above the rotors and the landing gear. The drowning rescue device body includes a life buoy, an air pipe, a carbon dioxide gas cylinder and an in-water automatic inflatable valve. The life buoy is arranged below the rotors and around the center of the vehicle body. The life buoy is connected with the in-water automatic inflatable valve through the air pipe. The in-water automatic inflatable valve is connected with an air outlet of the carbon dioxide gas cylinder. The carbon dioxide gas cylinder is fixed on the life buoy. The unmanned aerial vehicle drowning rescue device can conduct warning in advance to unmanned aerial vehicle drowning; it can be ensured that the unmanned aerial vehicle automatically conducts effective self recuing after the unmanned aerial vehicle is drowned; searching and positioning rescue implemented by a remote ground control device is facilitated; the loss of unmanned aerial vehicle drowning is reduced advantageously; and the search and rescue efficiency of unmanned aerial vehicle drowning is improved.