Pneumatic butterfly valve

The utility model relates to a pneumatic butterfly valve. The pneumatic butterfly valve comprises an upper valve rod, an upper shaft sleeve, a fastening pin, a butterfly plate, a lower valve rod, a valve seat, an O-shaped ring, a lower shaft sleeve, a valve body, a sealing gasket, a lower end cap and a pneumatic device connected with the top end of the upper valve rod. An embedding groove is formed in the outer surface of the valve body along the outer circumference; the valve seat is an elastic sealing valve seat. According to the pneumatic butterfly valve, the valve seat can automatically adjust the sealing pressure ratio, the embedding groove is formed in the outer surface of the valve body along the outer circumference, and the valve seat is embedded into the valve body with a gap, so that when in work, the valve body, the valve seat and the butterfly plate are tightly fit to achieve no leakage and good sealing performance; meanwhile, during rotation of the butterfly plate, the friction force and the star