Electrodeposition was employed to fabricate magnetite (Fe3O4) coated carbon fibers (MCCFs). Temperature and fiber surface pretreatment had a significant influence on the composition and morphology of Fe3O4 films. Uniform and compact Fe3O4 films were fabricated at 75 degrees C on both nitric acid treated and untreated carbon fibers, while the films prepared at 60 degrees C were continuous and rough. Microwave measurements of MCCF/paraffin composites (50 wt.% of MCCFs, pretreated carbon fibers as deposition substrates) were carried out in the 2-18 GHz frequency range. MCCFs prepared at 60 degrees C obtained a much higher loss factor than that prepared at 75 degrees C. However, the calculation results of reflection loss were very abnormal that MCCFs prepared at 60 degrees C almost had no absorption property. While MCCFs prepared at 75 degrees C exhibited a good absorption property and obtained -10 dB and -20 dB refection loss in wide matching thickness ranges (1.0-6.0 mm and 1.7-6.0 mm range, respectively). A secondary attenuation peak could also be observed when the thickness of MCCF/paraffin composite exceeded 4.0 mm. The minimum reflection loss was lower. (C) 2011 Elsevier B.V. All rights reserved.