The invention discloses an automatic inflation life 
buoy. The automatic inflation life 
buoy comprises an air bag and an inflation mechanism, wherein the inflation mechanism comprises a high-pressure gas storage 
steel cylinder, an ejector pin, an inflation 
nozzle and a movement 
assembly, the ejector pin and the movement 
assembly are both installed in the inflation 
nozzle, one end of the inflation 
nozzle communicates with the high-pressure gas storage 
steel cylinder, and the other end of the inflation nozzle communicates with the air bag; a layer of sealing film is arranged on a 
bottle opening of the high-pressure gas storage steel 
bottle, the ejector pin is fixed to the moving 
assembly, and the tip end of the ejector pin directly faces the 
bottle opening. The inflation nozzle is further provided with a water falling detection element, wherein when the water falling detection element detects that the air bag falls into water, the movement assembly moves towards the bottle opening of the high-pressure air storage steel bottle, so that the ejector pin punctures the sealing film. Through the design, the life 
buoy does not need to be inflated in advance, so that the size of the life buoy is reduced, and the life buoy is convenient to carry; meanwhile, automatic inflation is achieved when a person falls into water through the inflation mechanism, rapid rescue can be conducted on the person falling into water, the rescue speed is increased, and use convenience is improved.