The invention provides a lead screw top supporting device and a settlement control method. The lead screw top supporting device comprises anchor bars, an anchor plate, a bottom plate, a sliding lead screw, a top plate and a beam, wherein the two ends of the sliding lead screw are connected with the bottom plate and the top plate correspondingly; the bottom of the bottom plate is connected with the top of the anchor plate; and the bottom of the anchor plate is connected with the tops of the anchor bars. The anchor bars and the anchor plate are pre-embedded in a side pile or a middle column and/or a steel pipe column, and the top of the top plate is connected with the bottom of the beam. By using the lead screw top supporting device, settlement of an existing line structure can be effectively prevented, so that the settlement of the existing line structure can be limited within the preset small range, and the engineering cost can be reduced greatly.