Radiolytic characteristics of phytic acid by gamma irradiation were investigated, and the antioxidative activity between irradiated phytic acid and commonly used antioxidants including ascorbic acid, tocopherol and butylated hydroxyl anisole (BHA) was evaluated. Phytic acid sodium salt dissolved in a deionized distilled water was irradiated at 0, 5, 10, 15 and 20 kGy. It was found that the level of irradiation had an effects on the degree of degradation. After irradiation, stable DPPH radical scavenging capacity of phytic acid was newly observed, and it was significantly increased by dose-dependent manners (p<0.05). Antioxidant activity of phytic acid in the oil models was higher than that of the other antioxidant during storage, and phytic acid (400 $mu extrm{g}$/mL) irradiated at 20 kGy especially showed the highest antioxidative ability among the antioxidants tested during 3 weeks. Results indicated that irradiation induced the radiolysis of phytic acid in an aqueous model system, and the antiradical and antioxidative activities of irradiated phytic acid increased.