The invention discloses a propelling device of a tube cutting machine for a rubber tube. The propelling device of the tube cutting machine for the rubber tube comprises a mandrel, a propelling roller wheel and an ejecting rod, wherein the mandrel, the propelling roller wheel and the ejecting rod are matched with one another; the mandrel is cooperatively placed in the rubber tube, and is used for being propelled along with the rubber tube together; the propelling roller wheel is used for abutting and pressing the rubber tube and propelling the rubber tube to move along the axial direction through the rotation of the propelling roller wheel; the ejecting rod is arranged, along the axial direction, at a first predetermined position in front of the rubber tube relatively, and is used for inversely ejecting the mandrel when the mandrel is propelled along with the rubber tube together and is contacted with the mandrel; by stopping the ejecting rod in a second predetermined position after the ejecting rod enters the rubber tube during inverse ejecting, and then inversely retreating the ejecting rod to a third predetermined position, a knife blade of the tube cutting machine is enabled to cut off the rubber tube at a gap formed between the mandrel and the ejecting rod. The propelling device of the tube cutting machine for the rubber tube can be widely applied to the rapid and accurate cutoff of thin-wall rubber tubes, prevents the thin-wall rubber tubes from adhesion of tube walls, and improves the production efficiency.