In this paper, the microwave absorption properties of three different types of carbon nano materials such as U carbon, carbon nanotube and carbon black have been studied at the frequency band of 8 to 18 GHz. The complex permittivity of carbon nano materials/ paraffin composite with different weight fractions were measured at the frequency band of 8 to 18 GHz. The results show that the real and imaginary of the complex permittivity of the com posites were increased with filler weight and the increasing rates of the real and imaginary part with respect to the filler
weight were all different. These different rates have great effect on the thickness in the designing the single layer mi crowave absorbers. The match thickness of coating and the weight of filler were obtained by the Cole Cole plot. When 20% mass fraction carbon nanotubes were used with coating thickness of 1. 6 mm, the reflection loss is superior to -10 dB at 11. 2 to 15 GHz and the maximum reflection loss can reach -29. 6 dB.