Abstract: Irradiation damage effects of the epoxy resin 648 and epoxy nano-composites are studied in a simulated vacuum ultraviolet irradiation (VUV) condition with wavelength ranging from 5 nm to 200 nm. Experimental results of the mass loss, SEM and XPS show that nano-TiO2 particles lead to better resistance performance under the VUV. As compared with epoxy resin, the epoxy nano-composite shows significantly less mass loss, smaller flexural strength variation and a decrease of gas extraction with less gas component varieties after irradiation. What's more, no new carbon peak value has been found and the principal components of O ls peak value remain unchanged on the surface.