Underwater horizontal Christmas tree body center hole sealing device

The invention provides an underwater horizontal Christmas tree body center hole sealing device. The device comprises a device body consisting of an upper body and a lower body, and a mandrel consisting of an upper mandrel and a lower mandrel, wherein the mandrel is inserted into coaxial center holes of the upper body and the lower body; the outer side of the upper body is fixed with an outer lantern ring; the outer lantern ring and the outer wall of the upper body are formed to an annular groove; a sealing ring is arranged in the annular groove; the mandrel is coated with an inner lantern ring; the inner lantern ring is positioned between an upper mandrel sealing table shoulder of the upper mandrel and a lower mandrel table shoulder of the lower mandrel; the inner lantern ring and the sealing ring are connected through a fastening screw; the top end of the lower body and the bottom of the outer lantern ring are opposite at intervals; and the interval place is coated with a rubber sealing ring; a projection part is arranged at the outer side of the upper part of the sealing ring; and the inner wall of the sealing ring extends into the annular groove. The sealing device realizes the expansion sealing of the Christmas tree body center hole through single lifting, centering and base placing operations, reduces the underwater operation difficulty, and saves the underwater operation time and cost.