Abstract: A physics model possessed of medium interlayer composite shielding structure was proposed. The contrast experiments of monolayer shielding structure and composite interlayer shielding structure were designed and carried out. The ΔSE, the abbreviation for electromagnetic shielding effectiveness increments, of composite interlayer shielding structure was measured, while it was confirmed by Ватолцн multilayer electromagnetic shielding theory formulas. The electromagnetic shielding effectiveness of the composite interlayer shielding structure materials is obviously superior to that of the monolayer shielding structure materials. The preparation of the supple electromagnetic shielding materials possessed of composite interlayer shielding structure was performed by the method of electrochemical modification. Terylene non-woven and polytetrafluoroethylene, two kinds of synthetic fibres, were selected as research objects. The results show that the composite interlayer shielding structure-modified materials on synthetic fibre can be prepared by means of selecting objects and optimizing technics of electrochemical modification, which includes selecting different metallic plating layers, adjusting the impulse electroplate parameters, plating time, temperature and pH. Within the incident frequency range from 1MHz to 1000 MHz, this kind of modified synthetic fibre can meet different demands, and the maximum SE is up to 98dB. Not only is the composite interlayer shielding structure obtained, but also synthetic fibre materials are endowed with new electromagnetic characteristics, by way of the process of metallic modification.