A core barrel sealing structure includes a core barrel, a drilling machine outer barrel, a chain mail-type flap valve and a trigger mechanism. The flap valve includes a valve seat and a chain mail-type valve flap. The trigger mechanism includes a trigger inner barrel and a trigger block. The trigger block is arranged in a through hole in a sidewall of the trigger inner barrel, and an inner wall of the drilling machine outer barrel is provided with a recessed opening adapted to the trigger block. When the core barrel is located in the valve seat, the valve flap is opened by 90° and is located between the trigger inner barrel and the drilling machine outer barrel. When the core barrel is lifted upwards, the valve flap returns to a top face of the valve seat to make sealing contact with a sealing face of a valve opening.