Well mouth temporary closing plug

The invention discloses a well mouth temporary closing plug. The well mouth temporary closing plug comprises a central pipe, a liquid cylinder, a piston, a slip and an expansion capsule, wherein a thick-wall pipe with a through hole inside is adopted by the central pipe, the upper part and the lower part of the outer wall of the central pipe are equal in diameter, and a slip chamber which is in agroove shape and is used for containing the slip is arranged in the middle of the slip chamber; the liquid cylinder is cylindrical and is arranged at the lower half part of the outer wall of the central pipe in a sleeving mode and can freely move and seal in the axis direction of the outer wall of the central pipe; the piston in the liquid cylinder is sleeved and fixed on the outer side of the central pipe so that the liquid cylinder is divided into a low-pressure cavity at the lower part and a high-pressure cavity at the upper part; and a cone is designed between the slip and the liquid cylinder, the expansion capsul