The induced changes in the absorption edge and optical density by gamma-irradiation was measured for cellulose nitrate (CN). The optical absorption edge of CN is accurately determined as a function of absorbed dose up to 67.5 kGy. The results obtained show that the absorption edge and the optical density at a 520 nm wavelength were changed to a lower value by gamma-irradiation. The post-irradiation stability of the films under different conditions were studied. The results suggest the possible use of a cellulose nitrate film as a dosimeter for absorbed doses up to 67.5 kGy.