The invention discloses a method for eliminating molybdenum dioxide water-drop materials. The method is specifically implemented as follows: 1) molybdenum trioxide is selected as a raw material for preparation; 2) a vertical pipe part of a hydrogen return pipe is coated with a heat insulating material firstly and then fixed with a stainless steel screen, edges of the screen are required to be tightened with thin wires, finally, the outer part of the screen is coated with a thin aluminium-plastic panel, and the connecting port position of the aluminium-plastic panel is fixed with rivets; 3) the size of a pipe head part of the hydrogen return pipe is measured firstly, then a heat insulating cap is produced from a thin aluminium-plastic panel according to the measured size, a heat insulating material layer is attached to the inner wall of the heat insulating cap, and finally, the pipe head of the hydrogen return pipe is sleeved with the produced heat insulating cap; 4) five temperature zones in a four-horizontal-tube low-temperature reduction furnace are adjusted respectively; (5) selected molybdenum trioxide is placed in the adjusted four-horizontal-tube low-temperature reduction furnace for reversible hydrogen reduction treatment, and molybdenum dioxide is obtained finally. Molybdenum dioxide obtained with the method is relatively loose, and meanwhile, oversize molybdenum dioxide products are reduced.