In this study, an effective deposition of CuS on PAN film was proposed by an electroless plating method with the reduction agents NaHSO3 and Na2S2O3·5H2O and a chelating agent (triethanolamine, TEA). A variety of concentrations of TEA were added to obtain the anchoring effect and chelating effect in the electroless plating bath. The GIA-XRD and laser Raman analysis indicated that the deposited layer consisted of CuS. The mechanism of the copper sulfide (CuS) growth and the electromagnetic interference shielding effectiveness (EMI SE) of the composite were studied. It was found that the vinyl acetate remained in PAN substrate would be purged due to the swelling effect by TEA solution. Then the anchoring effect occurred due to the hydrogen bonding between the pits of PAN substrate and TEA. Consequently, the copper sulfide layer was deposited effectively by the electroless plating reaction. The swelling degree (Sd) was proposed and evaluated from the FT-IR spectra. The relationship between swelling degree of the PAN composite and TEA concentration (C) is expressed as: Sd = 0.07 + 1.00 × e^(− 15.15C). On the other hand, the FESEM micrograph showed that the average thickness of copper sulfide increased from 76 nm to 247 nm when the concentration of TEA increased from 0.00 M to 0.60 M. As a result, the EMI SE of the composites increased from 10–12 dB to 25–27 dB.