The article aims to explore the optimal concentration of arsenic trioxide (As2O3) on HepG2 of liver cancer cells, and the effect of As2O3 on the migration, invasion and apoptosis of HepG2 cells. In this study, the activity of HepG2 cells treated with 0, 1, 2, 4, 8, 16, 32 μmol/L As2O3 was tested by CCK-8 method, the semi-inhibitory concentration (IC50) was calculated, and the morphological changes of HepG2 cells were observed after the action of As2O3 at IC50 concentration for 12, 24, 48 h. The effect of As2O3 on cell migration and invasion ability was verified by wound healing experiment and Transwell invasion experiment. Western blot and qRT-PCR were used to detect the effects of As2O3 on the gene and protein expression levels related to cell migration, invasion and apoptosis. The results showed that, compared with the control group, the activity of HepG2 cells decreased with the increase of the concentration of As2O3 treatment, showing a dose-dependent effect, and its IC50 was 7.3 μmol/L. After 24 hours’ treatment with 8 μmol/L As2O3, HepG2 cells underwent significant apoptosis, and its migration and invasion abilities were significantly reduced. In addition, the protein expression levels of RhoA, Cdc42, Rac1 and matrix metalloproteinase-9 (MMP-9) were down-regulated, the protein and mRNA expression levels of anti-apoptotic gene Bcl-2 were significantly down-regulated, and the protein and mRNA expression levels of pro-apoptotic genes Bax and Caspase-3 were significantly up-regulated. The above results indicate that certain concentration of As2O3 can inhibit the migration and invasion of hepatocellular carcinoma cells and promote the apoptosis of hepatocellular carcinoma cells.