Mud gate valve is mainly used for mud circulation system of oil field or mine to control the mud flow and close. They are buttress threaded connected, easy for quick installation with great rigidity, safety and reliability. Parallel-type elastic sealing between valve seat and gate has good sealing performance and is easy to open. Connection of both ends of valve with pipes is sealed with spherical movable contacts, combined with the O rubber rings. Straightness of both ends is not so much important when installing this type of joints and with a good sealing performance.