A tube sealing machine for a flexible package includes in turn a bagging mechanism arranged on the rack, an intubation mechanism, a transmission mechanism, a molding mechanism and a bag connecting mechanism. The invention has the characteristics that the transmission mechanism comprises a movable stand, a reciprocating motion mechanism and at least one lifting mechanism; the lifting mechanism is fixed on the movable stand, the end of which is arranged movably on the rack; the movable stand connects the rack through the reciprocating motion mechanism; the side of at least one movable stand parallel to the movement direction of the reciprocating motion mechanism is provided with at least one flexible package holder. The invention has the beneficial effects to the prior art of simple structure, easy use, high-yield result, effective space-saving and great production-cost reduction.