Electroconductivity was to be imparted to poly(ethylene terephthalate) (PET) film by introducing Cu_xS, which is known as p-type semiconductor. This process can be devided into three stages as followed. (a)Graft copolymerization of acrylamide(AM) monomer, which is capable of coordinating to cuprous ion. (b) Adsorption of the cuprous ions to the coordinating sites, (c) Ion exchange reaction with active S atom to impregnate Cu_xS crystals. Optimum condition and kinetic reaction rate of the graft copolymerization were determined, and optimum pH condition for the introduction of Cu_xS was studied. Electrical resistivity of the Cu_xS-AM-g-PET film was 1,780Ω·cm, which was lower by factor of 10¹¹ than that of the original PET film. In the case of TSC of the Cu_xS-AM-g-PET electret, compared with TSC of the original PET electrets, the current generated by migrating of the mobile charges was predominant.