"This study analyzed the characteristics of PET film‘s surface deterioration by the surface treatment of ultraviolet and plasma. After ultraviolet and plasma surface treatment, the electrical insulation properties were investigated through the measurement of the surface potential decay and the surface resistivity with each treatment conditions. In addition the chemical properties were analyzed through the angle of contact and XPS. As far as UV treatment time increases, the surface potential properties of the corona charging device opened the polar group, activating the surface, and reduced the charge accumulation and quickened the potential decay. The surface resistivity and the surface potential decay properties with exposure decreased the electrical insulation ones. The angle of contact decreases as long as the investigation time lasted and the surface was activated with some reduced quantity. XPS analysis for chemical properties shows the relative increase of O1s peak by UV analysis, result considered as the decomposition of the combined print and formation of oxygen molecules containing hydroxyl or carboxyl groups. By plasma discharge treatment, electrical insulating properties have improved within 10 minutes of processing time due to the evaporation of low-molecular substances and surface cleaning and in case of time longer than 10 minutes the energy insulation properties decreased by the excessive discharge. Chemical analysis shows oxygen containing C-O, O = C-O's increase within the 10 minutes and within more than 10 minutes a relative decrease. Key words : PET, Surface deterioration, Ultraviolet, XPS"