The photoirradiation graft copolymerization of acrylic acid (AA) onto low density polyethylene (LDPE) film using benzophenone (BP) as a photosensitizer in an aqueous medium was investigated. The effect of monomer concentration, photosensitizer concentration, and reaction time on the graft yield were evaluated. The moisture regain and the degree of swelling of grafted film were higher than those of original film. As the graft yield was increased, the initial modulus and the tensile strength at yield point were increased but the elongation at break point, the crystallinity, and the heat of fusion were decreased. The elongation at yield point and the melting point were sustained without great difference.