On the basis of the single eccentric butterfly valve, further improved molding is currently the most widely used double eccentric butterfly valve. Its structural feature is that the axis of the valve stem deviates from the center of the butterfly plate and the center of the body. The effect of double eccentricity enables the butterfly plate to quickly detach from the seat after the valve is opened, which greatly eliminates unnecessary excessive squeezing and scraping between the butterfly plate and the valve seat, reduces the opening resistance, reduces wear and improves Seat life.