The FeSiBC amorphous powder cores were fabricated using powders of the FeSiBC amorphous ribbons which were mechanically crushed for a short time, and the relationship between magnetic properties and powder particle sizes was evaluated. The saturation magnetization Bs of the amorphous Fe82Si2B15C1 alloy was 1.62 T, which provided a superior dc-bias property for the powder cores. Meanwhile, a stable permeability up to high frequency range over 10 MHz and the low core loss of 400 kW/m3 at f = 50 kHz and Bm = 0.1 T were obtained. These excellent high-frequency magnetic properties of the FeSiBC amorphous powder cores could be attributed to the effective electrical insulation between the FeSiBC amorphous powders made by mechanical crushing.