Microwave absorbing material is currently being more and more widely applied in the world. However, conventional absorbent coating material cannot fulfill the complex current requirements of science and technology to have a wide absorption frequency band, and high absorption. This paper describes composite material plates with a multi-layer absorbing structure designed according to impedance-matching and attenuation principles, producing two- and three-layer absorbing structures. Twelve samples were made, containing graphite powder and manganese dioxide at varying concentrations. The results show that in the frequency range 8-18 GHz, the peak absorption of double-layer samples is -12.3dB, the effective bandwidth (R < -10 dB) is 1.8GHz. The absorption peak of three-layer samples is -18 dB, and the effective bandwidth (R < -10 dB) is 8GHz. The findings of this research are useful in improving the absorption bandwidth of absorbing material.