Carbon fibers (CFs) coated with Ni-X-P (X = W, Co-W or none) alloys were prepared by electroless plating. The morphology, crystal structure, and element composition of alloy-coated CFs were characterized by scanning electron microscopy, X-ray diffractometry, energy-dispersive spectrometry and microwave attenuation. The results showed that CFs were coated with a layer of alloy particles. P content in Ni-Co-W-P or Ni-W-P alloys was lower than that in Ni-P alloy, and coating alloy Ni-P was amorphous. After W or Co introduction, coating alloys exhibited crystal characteristics. MMW-attenuation performance analysis showed that the 3 mm wave attenuation performance of CFs/Ni-Co-W-P, CFs/Ni-W-P and CFs/Ni-P increased by 7.27 dBm, 4.88 dBm and 3.55 dBm, and the 8 mm wave attenuation effects increased by 11.61 dBm, 6.11 dBm, and 4.06 dBm respectively, compared with those of CFs. MMW-attenuation performance is attributable to the sample bulk resistivity and P content in the alloy, Moreover, an optimal weight gain value existed for the MMW-attenuation performance of alloy coated CFs. (C) 2015 Elsevier Ltd. All rights reserved.