Abstract: The traditional methods of surface treatment include gaseous, acid, solution, plasma, and electrolytic oxidation. ⁶⁰ Coγ ray irradation was newly used to increase the surface concentration of oxygen functionalities. The effect of such treatment upon fiber surface mechanical properties, chemistry, reactivity and roughness has been studied. X ray photoelectron spectroscope, electron microscope, Raman shift, and X ray diffraction were used to determine elemental compositional changes in fiber surface caused by irradiation. It was found that irradiation treatment improved the tensile strength, modulus, and fracture strain of carbon fiber, and surface oxygen is found in the distribution during irradiation dose 1×10²～1×10³Gy; irradiation process could change surface chemical constituents, leading to the promotion of surface activities. Maximum interlaminar shear strength of carbon fiber(dose 1×10³Gy)/epoxy corresponds to an increase of 31%.