The SiC powders by AI or N doping have been synthesized by combustion synthesis, using AI powder and NH 4 CI powder as the dopants and polytetrafluoroethylene as the chemical activator. Characterization by X-ray diffraction, Raman spectrometer, scanning electron microscopy and energy dispersive spectrometer demonstrates the formation of AI doped SiC, N doped SiC and the AI and N co-doped SiC solid solution powders, respectively. The electric permittivities of prepared powders have been determined in the frequency range of 8.2–12.4 GHz. It indicates that the electric permittivities of the prepared SiC powders have been improved by the pure AI or N doping and decrease by the AI and N co-doping. The paper presents a method to adjust dielectric property of SiC powders in the GHz range.