Based on the high strength of flake Al₂O₃ ceramic interlocking structure，Al₂O₃ porous ceramics with high porosity and graphite were prepared， and Ni particles were prepared by in-situ reduction in the porous skeleton to form a lightweight double-loss ceramic-based absorbing material. The effects of reduction temperature on the composition， microstructure，element distribution and microwave absorption properties of porous absorbing materials were studied by XRD，FE-SEM and EDS. Results concluded the following.The results show that Ni on the framework can be completely reduced when the temperatures is up to 700 ℃. The composite with a double loss function is composed of an interlocking Al₂O₃ matrix with graphite flakes embedded in it and Ni particles on the surface of pores. As the thickness of the composite is 6.5 mm，the reflection loss （RLmin） value is 35.01 dB and the effective bandwidth （RL ≤10 dB） is 1.75 GHz.Microwave absorption can be attributed to the conductive network formed by graphite flakes between flaky Al₂O₃ grains，as well as to the good impedance matching and polarization effect caused by the Ni particle-matrix interface.