The electromagnetic wave absorption properties of amorphous alloy-epoxy composites have been investigated utilizing various amorphous alloy particle sizes in quasi-microwave frequency. The composite fabricated with small sized particle (< 26 μm) only revealed good absorption properties above 20dB with a thin thickness less than 6 mm. As particle size decreased, absorber had thinner matching thickness mainly due to increasing matching frequency. Such a variation of matching frequency was resulted from resonance frequency variation. The magnetic relaxation of the composites with small particle (< 38 μm) was contributed to magnetic resonance induced by demagnetization field. The eddy current also affected on the magnetic relaxation of the composites with large particle (> 38 μm) due to their large conductivity.