The utility model discloses a winding tightener for a No.8 iron wire of a circuit. The device comprises an operation handle, a tightening adjusting rod, a symmetrical shell, a semicircular pressing ring, an extrusion iron wire pressing opening and an installation cavity. Wherein a mounting chamber is formed in the symmetrical shell; extrusion iron wire pressing openings are formed in the symmetrical shells in a front-back penetrating mode. The extrusion iron wire pressing opening is located in the center of the symmetrical shell. Semicircular brackets are fixedly mounted at the inner side topand the inner side bottom of the mounting chamber; a semicircular pressing ring is arranged between the top semicircular bracket and the bottom semicircular bracket; internal thread screw openings areformed in the left side inner wall and the right side inner wall of the mounting chamber; a tightening adjusting rod is arranged in the internal thread screw opening; one ends of outer twist sleevesare fixedly installed on the left side and the right side of the symmetrical shell, tightening adjusting rods are installed in the outer twist sleeves in a threaded mode, operation handles are fixedlyinstalled at the other ends of the outer twist sleeves, spring brackets are fixedly installed on the inner wall of the left side and the inner wall of the right side of the installation cavity, and compression springs are arranged on the spring brackets.