A remarkable host effect on the intercalation of CuCl2 in a molten salt system of CUCl2-KCl was observed. Even after 12 days in the molten salt at 380-degrees-C, no graphite intercalation compounds (GICs) were obtained from the graphite films prepared from a polyimide Kapton, while from highly oriented pyrolytic graphite and kish graphite with similar physical sizes, GICs were obtained within one day and from natural graphite flakes with the size of 400-mu-m, within two hours. The graphite film containing more defects (H-film) was transformed to the stage-2 GIC at 500-degrees by applying Cl2 pressure, but the more perfect film (O-film) did not under the same condition.