Abstract: In a system for feeding slivers from an aging room to a spinning frame room through tubes, a simple method is proposed, capable of maintaining a moisture content of sliver at a predetermined value even though the meandering state of sliver in the tube varies in accordance with the change of the operational conditions. A spinning frame room (1) and a sliver-aging room (5) are respectively provided on the first and second floors so that a sliver (8) is fed, through a tube (10) communicating both the rooms with each other, into a drafting mechanism (3) of a spinning frame installed in the spinning frame room (1). Air pressure in the aging room (5) is controlled to be higher than that in the spinning frame room (1) so that a downward air stream always generates in the tube (10) from the aging room (5) to the spinning frame room (1). An air-through aperture (9) with a damper (11) for adjusting an opening degree thereof is provided between the aging room (5) and the spinning frame room (1).