A balloon system for treating sinusitis or allergic rhinitis includes a central inner tube, a balloon to be filled and a balloon catheter outer tube, all of which axially extend. The central inner tube includes a distal end part and a proximal end part detachably connected with each other by a connector in an axial direction. A first end of the balloon is connected to the distal end part, and a second end of the balloon and the balloon catheter outer tube are detachably connected with each other by the connector. The balloon catheter outer tube is radially outwardly spaced from the proximal end part, and the connector includes a first grommet and a second grommet rotating coaxially and relatively fixed with each other in axial direction. Each of the first grommet and second grommet has at least one gas port.
