A novel method——Fenton/UV treatment, was used to modificate carbon nanotubes (CNTs) in our research. Effects of different molar ratios of Fenton reagents on the surface of CNTs were studied in our work. The purity of CNTs was investigated by TGA. The functional groups on the surface of CNTs were investigated by FTIR spectra, and the phase analysis of CNTs was investigated by X-ray diffraction analysis (XRD). The result show that it can introduce a great deal of hydroxyl groups onto the surface of carbon nanotubes, and almost never introduce impurities, when the molar ratio of Fe2+ and H2O2 is 1:40.