The invention discloses a bottle stopper suitable for bottles with various opening diameters. The bottle stopper comprises a gas bag (1) and a bottle cap (2). The bottle cap (2) comprises an outer shell (3) and an inner core (4). The inner core (4) is installed in the outer shell (3). The gas bag (1) is arranged in a gap between the inner core (4) and the outer shell (3) in a sleeved mode. A fan-shaped groove (5) is formed in the sidewall of the outer shell (3). The inner core (4) comprises a semilunar core block (6) and a deflation button (7). A square groove is formed in the middle of the semilunar core block (6). The deflation button (7) is connected with the square groove of the semilunar core block (6) through a spring. A deflation hole (9) is formed in the deflation button (7). The bottle stopper is simple in structure, convenient to use, capable of being suitable for the bottles with various opening diameters, good in sealing effect and high in repeating utilization rate.