The invention relates to a method for strengthening the compactness of a fine powdery material during vertical downward seal transportation. Ventilation openings are arranged into rows and columns along the axial direction of a transporting device (1); microporous metal plates or metal mesh plates cover the ventilation openings; the outer sides of the ventilation openings are sealed by sealing boxes; the outer walls of all the sealing boxes are connected with a vacuumizing tube (4) and collected on a two-way change valve (6); the two-way change valve (6) is connected with a vacuumizing machine unit (5); the sealing boxes and the microporous metal plates or the metal mesh plates form an independent vacuumizing device (3); and the vacuumizing machine unit (5) is started to vacuumize the two-way change valve (6). When the fine powdery material (2) naturally drops from the upper end and the lower end of the transporting device (1) to the inlet of deep-processing equipment (7), the vacuumizing device in the negative pressure state can absorb part of air and dust contained in the fine powdery material through the vacuumizing tube, and the compactness of the fine powdery material arriving at the inlet of the deep-processing equipment can be strengthened.