Abstract: Si/C/N nano whisker with certain composition was prepared by Chemical Vapor Deposition (CVD). The phase of the whisker was determined as β-SiC by XRD. TG analysis indicated that the whisker can resist oxidation up to 700℃. Dependence of the dielectric constant and loss tangent on the frequency was investigated. Based on the dielectric constant, mono and double layer absorber materials were designed, and the absorber property of the designed materials was estimated. The mechanism of microwave depletion by Si/C/N nano whisker was discussed, which is due to the dopant of nitrogen atoms in SiC lattice.