Abstract: A dust-bag previously pressing hook for a dust collecting machine is made of an elongate metal wire, wounded to have a combining portion in an upper portion, a coil portion in an intermediate portion and a straight portion in a lower portion. The combining portion is adjustably tightened or loosened on an annular ring of a wind exhaust tank, and the straight portion has an end hook to press against the annular wall by means of the torque coming from the coil portion. Then the end hook can previously press a dust bag moved up around the annular ring to let its mouth reach the end hook to be previously pressed by the end hook before the dust bag is secured tightly to be kept steady without falling down during subsequent dust collecting work.