Multi-walled carbon nanotubes (MWNTs) was irradiated with high-energy electron beams in different doses. The structure of irradiated MWNTs was characterized by Fourier transform infrared spectroscopy, X-ray energy dispersion spectroscopy，Raman spectroscopy and transmission electron microscopy. The results show that some oxygenous groups covalently bonded on the MWNTs. The nanotubes collapsed and even broke after irradiation. The effect of irradiated MWNTs on epoxy was studied and compared with that of non-irradiated MWNTs. It was found that the irradiated MWNTs were easier to be dispersed and could improve the glass transition temperature and initial decomposing temperature of epoxy resin. Addition of 0.5wt% MWNT irradiated with 170KGy into epoxy resin improved the glass transition temperature by 8 ℃ and the initial decomposing temperature by 14 ℃, respectively.