The invention provides a preparation method of a re-pressing-type PTC self-recovery safety device. The method comprises the following steps of (1) punching a first U-shaped through groove in a core plate; (2) covering the upper surface with a first upper insulating film and a piece of first upper electrode foil, covering the lower surface with a first lower insulating film and a piece of first lower electrode foil, carrying out lamination and removing the electrode foil; (3) punching a second U-shaped through groove in a mirror image of the first U-shaped through groove in the core plate, covering the upper surface with a second upper insulating film and a piece of second upper electrode foil and covering the lower surface with a second lower insulating film and a piece of second lower electrode foil and carrying out lamination; and (4) etching dicing lines on the surface, corresponding to the first U-shaped through groove and the second U-shaped through groove, of the core plate, carrying out punching on the upper surface to the upper surface of the second upper electrode foil and filling holes with conductive metal, carrying out punching on the lower surface to the lower surfaceof the second lower electrode foil and filling the holes with the conductive metal and carrying out cutting along the dicing lines to obtain the safety device. The safety device prepared through the preparation method is good in resistance consistency, low in rejection rate, high in stability and small in long-laid resistance variability.