The invention discloses a medicine sealing device capable of automatically controlling opening and closing and a sealing method. The medicine sealing device comprises a bottle body and a bottle plug which is movably connected with the bottle body, wherein a sealing mechanism is arranged between the bottle neck of the bottle body and the bottle plug, and comprises a blind hole formed in the bottle plug, a lower support body arranged on the inner bottom of the blind hole and provided with a trapezoidal longitudinal section, a rubber barrel located in the blind hole, an upper support body provided with a through hole, and a screw rod provided with a press sheet; a threaded groove is formed in the lower support body; the screw rod penetrates through the upper support body and the rubber barrel to be connected with the lower support body; a conical structure is arranged on the lower end of the screw rod; a drive motor is arranged on the upper part of the bottle plug; a rotating shaft of the drive motor is connected with the screw rod by a coupling; and a lower support body centralizing guide mechanism is arranged on the inner bottom of the blind hole. The medicine sealing device capable of automatically controlling opening and closing medicine and the sealing method have the advantages that the sealing effect is good; time and labor are saved during opening; medicine is convenient to take; and sealing is facilitated after the medicine is taken.