In order to explore and compare the cytotoxicity induced by nano-SiO2 and normal SiO2 particles, Hela cells were exposed to these two particles with different concentrations(0.05、0.1、0.2、0.4、0.8、1.6μg·μL-1) for 12h. The MTT assay was applied to measure the cytotoxicity. Results showed that, low concentration(≤0.2μg·μL-1) nano-SiO2 and normal SiO2 had no significant toxicity to Hela cells(p0.05). While in the high concentration, nano-SiO2 (≥0.4μg·μL-1) and normal SiO2(≥0.8μg·μL-1)had significant toxicity to Hela cells(p0.01), and the cytotoxicity increased with the increase of concentrations. Nano-SiO2 induced greater cytotoxicity than normal SiO2 at the same concentration(p0.05) when the concentration was above 0.4μg·μL-1. It was concluded that both nano-SiO2 and normal SiO2 particles could induce cytotoxicity to Hela cells, and nano-SiO2 showed greater cytotoxicity than normal SiO2 particles. Low concentration(≤0.2μg·μL-1) nano-SiO2 and normal SiO2 were well biocompatible with Hela cells, and this characteristic probably had a good application foreground in biomedical research.