Continuous surface treatment of PET film was carried out to improve its hydrophilicity and wettability by the irradiation of UV light. The effects of spectral irradiance and irradiant energy density on the surface energy of the treated films were investigated using three types of UV bulbs and measuring contact angles of three different test liquids. Surface energy of PET film was substantially increased by UV irradiation generated by a continuous UV curing machine. From ATR analysis, the increased hydrophilicity of irradiated films may be attributed to phenolic hydroxyl and carboxylic acid groups introduced by chain scission and oxidation. The ageing and water-rinsing after surface treatment had little influence on the surface energy of the irradiated film, showing excellent durability of the modification. The dyeability of the treated films to basic dyes were significantly improved by electrostatic and acid-base interaction between cationic dye molecules and the anionic film surface.