To have a better understanding on radioprotection mechanisms of fullerenol, surviving fraction was counted for ,Stylonychia mytilus, irradiated by ,60,Co γ-rays to 100—2000Gy, with fullerenol of 0.10mg mL,-1, being added to some of the sample groups, on the fifth day after the irradiation. Morphologic and superstructure changes were observed with optic microscope and transmission electricity microscope. Superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), and lipofusion (LIP) levels were measured. The results showed that fullerenols could obviously enhance surviving fractions of the ,Stylonychia mytilus, irradiated to up to 1500Gy. This indicates that the radioprotection is related to both fullerenols concentration and degree of the damages caused by the γ-ray exposure. Microscopic images revealed characteristics of the radiation damages with celluar and subcelluar structures of the ,Stylonychia mytilus, and these gave additional evidence for radioprotection of fullerenol. The activity of SOD and CAT of the irradiated groups are lower than the control group without irradiation (,p,<,0.01). The presence of fullerenol obviously increased SOD and CAT activities of the irradiated group, in comparison to the control groups without fullerenol or without irradiation, with ,p,<,0.01 in both cases. The MDA and LIP levels of the fullerenol-added and irradiated groups lowered significantly than the control groups (,p,<,0.01, p,<,0.05, respectively). The study shows that fullerenols have a good protection for the ,Stylonychia mytilus, from theγ-ray exposure. Protective effect of fullerenols on damages induced by γ-rays seems to be mediated, at least in part, through their antioxidantive and radical scavenger activities.