In this study, a copper sulfide layer was instantaneously coated on the polyacrylonitrile (PAN) by an electroless plating method with the reduction agents NaHSO3 and Na2S2O3 center dot 5H(2)O and a chelating agent (ethylenediaminetetraacetic acid, EDTA). A variety of concentrations of EDTA was added to obtain the anchoring effect and chelating effect in the electroless plating bath. The mechanism of the Cux(x = 1,2)S growth and the electromagnetic interference shielding effectiveness (EMI SE) of the composite were studied. It was found that the vinyl acetate was residual in PAN substrate would be purged due to the swelling effect by EDTA solution. Then, the anchoring effect occurred due to the hydrogen bonding between the pits of PAN substrate and the chelating agent. Consequently, the copper sulfide layer deposited successfully by the electroless plating reacted upon EDTA. The swelling degree (S-d) was proposed and evaluated from the FTIR spectra. The relationship between swelling degree of the PAN composite and EDTA concentration (C) is expressed as follows: S-d = 0.13 + 0.90 x e((-15.15C)). On the other hand, the FESEM micrograph showed that the average thickness of copper sulfide increased from 76 to 383 nm when the concentration of EDTA increased from 0.00 to 0.20M. For this reason, the EMI SE of the composites increased from 10-12 dB to 20-23 dB. The GIA-XRD and laser Raman analysis indicated that the deposited layer consisted of CuS and Cu2S. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 570-578, 2010