Radiation processing is a high efficient, energy-saving and environment-friendly technology, and has been widely used to modify material interfaces. In this paper, simultaneous γ-ray radiation graft copolymerization was used to improve surface property of carbon fibers (CF) with phenolic aldehyde/ethyl alcohol solutions of different concentrations. The CF samples treated with the solutions were irradiated by ,60,Co γ-rays to 30kGy at a dose rate of 4.8kGy/h. The grafted samples were characterized with atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). And interlaminar shear strength (ILSS) of the composite reinforced by the grafted CFs was compared to the control (composites reinforced by the virgin CFs). The AFM measurement revealed obvious morphology changes of the grafted CF. The XPS spectra showed that the oxygen/carbon ratio and quantity of oxygen functional groups were enhanced efficiently by the radiation graft copolymerization. And interfacial performance of the composite reinforced by the grafted CFs was enhanced significantly.