The SiC nanotubes were synthesized on porous Si3N4 matrix by polysilazane immersion-pyrolysis.The β-SiC and free C contents increased with the increasing dipping times,which cause some clear vibration and loss peaks of the dielectric constant patts emerged at around 12.9 GHz and 14.7 GHz in the samples of 20 wt％ and 30 wt％ benzoic acid,respectively.The reflectivity of the obtained ceramics were-7dB ～-10dB from the frequency of 8GHz-18 GHz,which means that the amount of 80％-90％ electromagnetic wave could be attenuated.The ceramics containing 40 wt％ benzoic acid showed the high loss,low reflectivity and a wide absorbing band,indicating the high absorbing efficiency and good dielectric properties.