Abstract： Objective To investigate the radio-protective effects of carboxy fullerene C3(C3)on AHH-1 cell.Methods C3 was prepared by chemical synthesis and trypan blue rejection test was performed to detect the cytotoxicity of AHH-1 cell.Then different concentration of C3 Wag used to treat AHH-1 cells radiated with 60Co γ ray.Annexin-V/PI staining and flow cytometry assay were applied to assess the proliferation and apoptosis of cell after irradiation.Results In cell culture system,C3 showed little toxicity to AHH-1 cells with little change of trypan blue rejection rate within the drug concentration range 0-400 mg/L(P＞0.05).We found in this study C3 had good radio-protection effects to AHH-1 cell irradiated with 1-8 Gy γ-ray.When the concentration was 10 mg/L,C3 showed protective effects to AHH-1 cell irradiated with 4 Gy γ-ray,which was enhanced with increasing C3 concentration.When the final concentration reached 200-400 mg/L,the cell survival rate after irradiation was similar to that of non-irradiated control cell(P＞0.05).And the irradiation induced apoptosis and death rate were significantly lower than those of single irradiated group cells(P＜0.01).Moreover,the radio-protective effects of C3 were time-dependant,and the best protection effects were observed when the C3 was administered before irradiation(0-24 h).Conclusions C3 has good radioprotective effects to AHH-1 cell,which is dose-dependent,and the higher concentration of C3 is,the better protective effect showes.in the effective drug concentration range of this study.C3 does little harm on the survival rate of AHH-1 cell which suggests that C3 as a novel promising radio-protectant deserve to be fuaher investigated.