Abstract: Carbon fibers were plated with the electroless nickel plating method, the micro-morphology of nickel-plated carbon fibers, the microstructure and composition of coatings were studied with SEM, EDX, XRD. The conductivities of nickel-plated carbon fibers were tested with broadband resistance voltage instrument. The nickel-plated carbon fibers/epoxy resin conductive composites with volume percentage of 2.5%, 5%, 7.5%, 10% were made by mixing method, the shielding effectiveness of these composites was tested by shielding enclosure method. Results show that after nickel plating, a lay of uniform nickel coating is formed on the surface of carbon fibers. The quality fraction of nickel in the coatings is about 94%. The resistances of nickel plated carbon fibers are only 1/54 of original carbon fibers. The shielding effectiveness of the nickel coated carbon fibers/epoxy resin composites is higher than that of original carbon fibers. The shielding effectiveness of the composites increases with the increasing of nickel-plated carbon fibers content. On low frequency(~kHz), the shielding effectiveness of the composites depends on material intrinsic parameters, and the shielding effectiveness is almost independent on the nickel-plated carbon fibers content. While on high and intermediate frequency(~MHz, ~GHz), the shielding effectiveness is related with resistivity of the nickel coated carbon fibers/epoxy resin composites.