The invention discloses a mechanical press screw thread fastening device and method. The mechanical press screw thread fastening device comprises a plurality of thread connecting rods and nuts, wherein the thread connecting rods are arranged on the end face of a flange plate of a screw thread in the circumferential direction of the medial axis of the screw rod; the nuts are arranged on the threadconnecting rods in a penetrating manner; a heating passage is arranged in each of the thread connecting rods; the thread connecting rods sequentially penetrate through thread holes in the screw sleeveand the guide column to be connected; a stretching structure capable of stretching the thread connecting rods is arranged on the flange plate of the screw sleeve; a plurality of symmetrical key grooves are formed in the threaded holes in the screw sleeve in the circumferential direction; locking key plates matched with the key grooves are arranged among the thread connecting rods and the screw sleeve; and fan-shaped locking press cakes are arranged in the thread holes in the guide column. The thread connecting rods are heated and stretched, and are matched with the locking key plates too lockthe nut, and the fan-shaped locking press cakes are utilized to lock the root part of a stud-bolt, so that the pretightening force between the thread connecting rods and the screw sleeve and betweenthe thread connecting rods and the guide column is increased; and locking key plates connect and lock the screw sleeve and the nut to enhance the fastening effect.