In this paper the carboxyl-fullerene C,3, was synthesized using Bingle’s cycloaddition reaction and its molecular structure was characterized by ,1,H-NMR,13,C-NMR and MS-ESI. The free radical scavenging ability of C,3, was confirmed by ESR in Fenton system. CCK-8 assay, AnnexinV/PI staining and flow cytometry assay were performed to evaluate the cell survival rate, apoptosis and cell cycle alteration after γ-ray irradiation respectively. The results showed that C,3, has excellent free radical scavenging ability in Fenton system with a scavenging rate 93 % at the concentration of 1000 mg/L. It has been revealed that C,3, has good radioprotection effects to AHH-1 and HIEC cells from radiation damage induced by 1~12 Gy γ-rays in evidence of higher survival and lower apoptosis rate of the cell. The mechanism may be related to its ability of scavenging free radicals.