The changes of magnetic properties with annealing temperature were studied in the amorphous Fe 8 6 . 7 Zr 3 . 3 B 4 Ag 6 thin film. The thin films were deposited by a DC magnetron sputtering method, annealed at 300-700 o C for 1h in vacuum under a field of 1.5kOe parallel to the film plane, and then furnace-cooled. As a result, it has been found that the Ag addition to Fe-Zr-B amorphous thin films resulted in the decrease of crystallization temperature to 400 o C due to promoted crystallization ability. Also, it gave rise to formation of fine BCC α-Fe crystalline precipitates with a grain size smaller than 10nm in the amorphous matrix near 400 o C, and led to prominent enhancement in the magnetic properties of the Fe 8 6 . 7 Zr 3 . 3 B 4 Ag 6 thin films. Significantly, excellent magnetic properties such as a saturation magnetization of 1.7T, a coercive force of 1Oe and a permeability of 7800 at 50MHz were obtained in the amorphous Fe 8 6 . 7 Zr 3 . 3 B 4 Ag 6 thin film containing 7.2nm-size BCC α-Fe, which was annealed at 400 o C. Also, core loss of 1.4Wcm - 3 (B m =0.1T) at 1MHz in the thin film was obtained, and it is a much lower value than had been obtained in any existing soft magnetic materials. Such excellent properties are inferred to originate from the uniform dispersion of nano-size BCC α-Fe in the amorphous matrix.