Research on carbon nanotubes has expanded to nearly every area,and we could believe that it will be very useful to radiotherapy,a classic and efficient method of cancer treatment.Through extreme oxidation by peroxide,many groups such as hydroxy and carboxide appeared on the CNTs out surface,these groups can be easily changed into free radicals with large concentration under very low dose radiation.Associated with the high uptake by cancer cells these superoxidized CNTs will result in lethal injury to cancer tissue.We have prepared superoxidized CNTs by using ammonium persulfate and added it into cell culture medium.Finally we find it has the 8.7 times higher killing efficacy than the control one.Thus we concluded that superoxidized CNTs could be regarded as a very promising radiosensitizer overmatching the current clinical adopted Sodium Glycididazole only after it was functionalized by cancer target materials.