The utility model discloses a three -phase solid is rolled up unshakable in one's determinationly and the book iron core transformer, and the three single frame iron core that includes unshakable in one's determination is rolled up to this three -phase solid, and every single frame iron core cup joints formation by the multilayer lamination in proper order, all is equipped with the fracture seam on every layer of lamination of every single frame iron core, the fracture seam sets up is close to the position of upper yoke on the upper portion of stem unshakable in one's determination, and has an angle of inclination between fracture seam and the horizontal plane. The three -dimensional book of this three -phase performance unshakable in one's determination is close with traditional three -dimensional iron core of rolling up, need not taking the iron core to wind during its coiling and makes the wire winding become extremely convenient.