Grafting of acrylic acid(AA) onto isotactic polypropylene(iPP) film was investigated. Graft polymerization was carried out with ultraviolet(UV) irradiation method in the presence of benzophenone(BP) as a photoseensitizer. The most suitable reaction temperature was 7$0^{circ}C$ for the maximum grafting yield. Moisture regain and swelling properties of grafted films were markedly improved by the grafting of AA monomer. The crystallinity of grafted film was evaluated from dsc and X-ray diffraction measurement. It was found that the crystallinity decreased with increasing grafting yield up to 100% but decreased sharply above 100%. Infrared spectra also showed the decrease of crystallinity. Mechanical properties of grafting films were also examined by tensile testing machine.