Damage effects of CF/EP under the vacuum ultraviolet radiation were studied using a gas-jet type of vacuum ultraviolet simulator (BYO)for simulating the ultraviolet radiation in real space. Results of mass loss, inter - layer shear strength, SEM and XRD shown that obvious mass loss of CF/EP was produced and the surface was suffered a severe damage under vacuum ultraviolet. The inter- layer shear strength slightly increased at the original period of radiation and presents a remarkable decreasing trend as increasing the radiation time. The carbon fibers have no obvious changes and serve as a protector for epoxy matrix under the vacuum ultraviolet radiation.