Diamond-like carbon films, prepared by rf glow discharge method on glass substrate, were irradiated by γ rays. The as-deposited and irradiated films were characterized by Raman spectroscopy, electrical resistivity, and infrared transmittance. It is shown that the irradiation of the γ ray can lead to the break and decrease of SP3C-H and SP2C-H bonds, the increase of SP3C-C bonds slightly, and induced hydrogen recombination with H2 molecule, subsequently diffusing to the surface of the film. When the irradiation dose of the γ ray reached 10×104 Gy, the numbers of SP3C-H bonds were decreased by about 50%. There was the tendency of ascending in resistivity, the diamond-like character of films is more apparent, and the structure of DLC films was modified when irradiated by γ. The irradiation mechanisms are briefly discussed.