Abstract: This study investigated the acute antioxidative effects of multiscale nano-SiO2 in organ of specific pathogen free (SPF) mice of the ICR strain. The mice were randomly divided into five groups and were intravenously injected with a multiscale nanoSiO2 suspension except for the control group. After 72 h observation, all the mice were killed and their liver, kidney and spleen extracts were measured for total protein (TP)，superoxide dismutase (T-SOD), glutathione peroxidase (GSH-PX）and malondialdehyde (MDA). The results show that 20.3 nm SiO2 has the most toxic effect to mice, followed by 49.8 nm and 80.0 nm SiO2. The 800.0 nm SiO2 has the weakest toxicity. This finding fully illustrates the scale effect of nanoscale particles. Statistical analysis shows that oxidative damage can possibly occur in liver（P＜0.01）. MDA is the most sensitive indicators in antioxidant enzyme system. The difference is very obvious（P＜0.01）,but other indexes don't perform their significant difference (P>0.05).