Diamond-like carbon (DLC) films have been deposited on glass substrates using radio-frequency (rf) plasma deposition method. γ-ray, ultraviolet (UV) ray were used to irradiate the DLC films. Raman spectroscopy and infrared (IR)spectroscopy were used to characterize the changing characteristics of SP3C-H bond and hydrogen content in the films due to the irradiations. These results show that the damage degrees induced by the UV ray on the SP3C-H bond are much stronger than that by the γ-ray. When the irradiation dose of γ-ray reaches 10×104 Gy, the SP3C-H bond reduces about 50% in number. The square electrical resistance of the films is reduced due to the irradiation of UV ray and this is caused by severe oxidation of the films. By using the results on optical gap of the films and the fully constrained network theory, the hydrogen content in the as-deposited films is estimated to be 10-25at.%.