The utility model relates to a center -type butterfly valve, including valve body, valve disc, valve seat ring and valve rod, its characterized in that distributes on the valve body has the observation hole, observes the outer through -hole to the valve body in of kong weicong valve body, observes downthehole port and feeds through with the valve body inner chamber, is connected with on the outer port and seals the screw. Its characteristics are: through the observation hole that sets up on the valve body, leak in the discovery valve that can be timely, accurate to the valve has been realized in time maintaining or changing. Its simple structure easily makes, the maintenance of being convenient for.