In this study, magnetic Fe3O4 particles were prepared from copper/iron ore cider by precipitation oxidization method. The yield of Fe was 82.6 at%. XRD, TEM, SEM, EDS and microwave network analyzer were used to characterize the particles. The results showed that Fe3O4 particles were well crystallized and possessed an octahedral morphology, and the crystal size was about 200 nm; the sample with 70 wt% Fe3O4 exhibited the optimal absorbing ability, the minimum reflection loss was -42.7 dB at 14.08 GHz and the bandwidth less than 10 dB was about 4.2 GHz when the sample thickness was 1.9 mm. It was clearly demonstrated that the Fe3O4 particles prepared from copper/iron ore cider could be used as an effective microwave absorbing material. (C) 2009 Elsevier Ltd. All rights reserved.