The static magnetic characteristics and microstructures of FeCuNbSiB fibres fabricated by the melt spun process, have been studied in this paper. The electromagnetic parameters (relative complex permittivity and permeability) of the composite have been also investigated using fibres heat treated at 673 K for 1 h in X band (8.2 GHz~12.4 GHz). In the range of 2 GHz~4 GHz, the effect of the content of the randomly oriented fibres in the composites (fibres + spherical magnetic particles + epoxy) on the electromagnetic parameters has been studied. The results show that the electromagnetic parameters can be improved effectively with an appropriate content of FeCuNbSiB fibres.