Graft copolymerization with acrylic acid(AA) onto high density polyethylene(HDPE)film by using benzophenone(BP) as a photosensitizer in an aqueous medium was carried out under ultraviolet(UV) irradiation. The infrared spectrum of the grafted HDPE film with acrylic acid shows characteristic bands of carboxylic acid, which demonstrates that grafting occured. The effects of various reaction parameters involving monomer concentration, photosensitizer concentration, reaction time and reaction temperature were investigated. As monomer concentration and photosensitizer concentration were increased, the graft yield was increased up to limiting value and after decreased. And also the graft yield was found to increase by increasing the reaction time and temperature. It was shown that the contact angle was decreased and the degree of swelling was increased with increasing the graft yield.