The amorphous silicon oxycarbide powders containing in situ-grown single-crystal silicon carbide nanowires were fabricated via the pyrolysis of a polymeric precursor with ferrocene as the catalyst. The nanowires, with lengths of several micrometers and diameters of 10-100 nm, were composed of single-crystal β-SiC along the <111> growth direction and uniformly dispersed in the composite powders. The growth mechanism of silicon carbide nanowires was explored by analyzing the microstructure of the silicon carbide nanowires. The dielectric properties of the composite ceramic powders were studied, which demonstrates that silicon carbide nanowires can be used to adjust the electrical of the composite and a high nanowire content can result in a large real and imaginary part of permittivity.