Carbon fibers reinforced Si(3)N(4)composites with SiC nanofiber interphase (C-f/SiCNFs/Si3N4) were prepared by combining catalysis chemical vapor deposition and gel-casting process. Microstructures, mechanical properties, and electromagnetic wave absorption properties within X-band at 25 degrees C-800 degrees C of C-f/SiCNFs/Si(3)N(4)composites were investigated. Results show that SiC nanofibers are combined well with Si(3)N(4)matrix and carbon fibers, the fracture toughness is thus increased more than double from 3.51 MPa center dot m(1/2)of the Si(3)N(4)ceramic to 7.23 MPa center dot m(1/2)of the as-prepared composites. As the temperature increases from 25 degrees C to 800 degrees C, C-f/SiCNFs/Si(3)N(4)composites show a temperature-dependent complex permittivity, attenuation constant, and impedance. The relatively high attenuation capability of C-f/SiCNFs/Si(3)N(4)composites at elevated temperature results in a great minimum reflection loss of -20.3 dB at 800 degrees C with a thin thickness of 2.0 mm. The superior electromagnetic wave absorption performance mainly originates from conductive loss, multi-reflection, and strong polarization formed by the combined effects of carbon fibers and SiC nanofibers.