The invention relates to a tube supplying device of assembly equipment of a disposable infusion set and a control method thereof. The tube supplying device comprises a tube supplying length controller and a rotating shaft for placing an infusion tube roll, wherein the rotating shaft is connected with a step motor; the tube supplying length controller is arranged between the rotating shaft and the assembly equipment of the disposable infusion set and provided with a longitudinal guide pillar; a gravity slide block is arranged on the guide pillar; a position sensor is arranged between the guide pillar and the gravity slide block; and both the step motor and the position sensor are connected with the controller. The tube supplying device has the characteristics that an infusion tube which is loosened for later use is appropriate in the degree of tightness, does not deform or twine and the like.