Abstract: Multi-walled carbon nanotubes (MWCNTs) were irradiated to different doses by high-energy electron beams. The structure of the irradiated MWCNTs was characterized by Fourier transform infrared spectroscopy, X-ray energy dispersion spectroscopy，Raman spectroscopy and transmission electron microscopy. MWCNT/epoxy composites were prepared by a cast-molding method. The effect of the irradiation on the properties of the composites was studied by scanning electron microscopy, thermogravimetry and dynamic mechanical analysis. Results showed that oxygen-containing groups were covalently bonded on the MWCNTs. The MWCNTs were collapsed and even broken after irradiation. The percentage of the oxygen-containing groups had a maximum of 4% at a radiation dose of 170kGy. It was found that the irradiated MWCNTs could be easily dispersed in epoxy resin. Addition of 0.5mass% MWCNTs irradiated with 170kGy to epoxy resin improved the glass transition temperature and the initial decomposition temperature by 8 and 14℃, respectively.