The utility model discloses a retractable bottle cap sealing structure which comprises a fixed bottle mouth, a retractable structure and a bottle cap; a bottle mouth upper protrusion ring and a bottle mouth lower protrusion ring are arranged at the upper part and the lower part of the inner side of the fixed bottle mouth respectively; a retractable structure upper protrusion ring and a retractable structure lower protrusion ring are arranged at the upper part and the lower part of the outer side of the retractable structure respectively; a protrusion is arranged on the inner side of the bottle cap and at the position close to the top end; the telescopic structure upper protrusion ring is in contact with the protrusion; the telescopic structure lower protrusion ring is in contact with the bottle mouth upper protrusion ring and the bottle mouth lower protrusion ring so as to restrict the maximum displacement of the retractable structure and prevent the retractable structure from dropping off or falling into the bottle; the bottle mouth upper protrusion ring is in close contact with the retractable structure to prevent liquid from flowing out. According to the utility model, the retractable structure of the is hidden inside the fixed bottle mouth to be prevented from being in contact with the outside; after the bottle cap is unscrewed, the retractable part is pulled out directly, and then a hand is prevented from touching the bottle mouth, so that secondary pollution caused to the bottle mouth can be prevented.