Abstract: To investigate the relationship between the structure and the electromagnetic wave absorption properties of the absorbing material, the inorganic foam absorbing material was used as the basic material. The effect of impedance matching on the absorption properties was studied by multi-layer composite structure. When the material was two-layer composite structure of "transparent layer/absorption layer", the reflectivity of material presented as below -10.0 dB in the band of 2.0-18.0 GHz, and the maximum attenuation loss peak was -21.5 dB at 12.7 GHz. The effect of the material surface structure on the absorption properties was studied by the treatments of pyramid structure and cone structure. Results show that the surface treatment can significantly improve the material absorption properties, furthermore, the absorption properties of pyramid strucure is better than that of the cone structure. The effective absorbing bandwidth (R < -10.0 dB) of the pyramid structure with an array of 5×5 is 15.3 GHz, and the minimum reflectivity is -43.4 dB at 9.4 GHz. Also, the effective absorbing bandwidth (R < -10.0 dB) of the pyramid structure with an array of 8×8 is 18 GHz, and the average reflectivity is -34.5 dB.