Abstract: A combined structure for air-conditioning ventilation comprises a tee connector (1), an easy connector (40), and a caliber adapter (30). The tee connector (1) comprises a tubular adjustable part (10) at its cylindrical tube (3) for outflow ventilation. The caliber adapter (30) may be installed at the inflow cylindrical tube (14) of the tee connector (1). By clamping the snap-fit points of the easy connector (40) into the snap-fit points (7) that is located on a first cylindrical tube (3) of the tee connector (1), the easy connector (40) may be installed at the first cylindrical tube (3). The resulting combined structure can be easily installed and used, and can have its parts easily switched.