The invention discloses a cork. The cork comprises a T-shaped cork body. An air bag made from elastic polyurethane materials is arranged in the cork body. A connecting hole is formed in the top of an accommodating cavity of the air bag and the top of the cork body. A needle is attached to the surface of the top of the cork body. The air bag is arranged in the cork body for supporting, the diameter of the cork body can be kept larger than that of a wine bottle in an initial stage, so that the sealing effect of the wine bottle is guaranteed. When the wine bottle needs to be opened, the needle is used for piercing the air bag, and the cork can be easily unplugged without assistance of an external tool since the internal space of the cork shrinks and a large shrinking room is provided for the cork.