Abstract: To obtain good dispersion and interface characteristics in epoxy resin ( EP) composites, carbon nanotubes (CNTs) were firstly hydroxylated with Fenton reagent treatment, and then surface-modified with silane coupling agent KH550, KH560, KH570 and titanate coupling agent NDZ2201, respectively. The influence of coupling agent modification on the properties of CNTs/EP composites was investigated by SEM, DSC, TGA and impedance analyzer. The experimental results show that Fenton reagent treatment and modification using four kinds of coupling agents can all obviously improve the dispersion of CNTs, glass transition temperature (T_g) and thermal stability of EP. All coupling agent modifications are more effective than the Fenton reagent treatment. However, these modifications can significantly reduce the electric conductivity, permittivity and dielectric loss of the composites. Among the four kinds of coupling agent modification, the composite modified by KH560 shows the highest T_g, the best thermal stability and electric conductivity, high permittivity and low dielectric loss.