Abstract: A single-layer absorber st ructure containing randomly dist ributed discrete macro-inclusions was designedby isolating the conductive medium in the absorbing mat rix , and the effects of carbon black (CB) content and samplethickness on the reflection loss as well as microwave loss mechanism were analyzed. The test results show that ,with increasing the carbon black content of the discrete particles in the slab absorber , the reflection loss increases ina f requency range of 8～18 GHz. When the mass f raction of CB get s to 30 % , the reflection loss was above - 10 dBin 8. 5～18 GHz and above - 15 dB in 15～18 GHz. Especially , when the thickness of the discrete slab absorberreaches 20 mm , the reflection loss was above - 15 dB in 8～18 GHz. The result s indicate that the discrete st ructureexhibit s the optimum absorptivity in 8～18 GHz compared with that of the compact sample , and it is a potentialexcellent absorber.