Flange type ventilating butterfly valve is made of steel plate welding. It has the characteristics of short size, light weight and easy installation. The valve has the advantages of small driving torque, flexible opening and closing, and easy operation. The oil seal ring is arranged on the valve body, and no visible clearance exists between the sealing seal, and the leakage rate is small. The expansion gap between the butterfly plate and the valve body is large, which can effectively prevent the stuck phenomenon caused by the thermal expansion and contraction. The valve can be equipped with a variety of driving devices, such as manual device, worm gear drive, pneumatic device, electric device. Ventilation butterfly valve is widely used in metallurgy, petrochemical, power, building materials, mines and other industrial pipelines, control or regulate the role of medium gas.