Abstract: 【Abstract】 Objective To determine the effect of autophagy on the apoptosis of hepatocellular carcinoma cells induced by arsenic trioxide (ATO). Methods Hepatocellular carcinoma HepG2 cells were exposed to ATO. The cell viability was detected by MTT after adjustments for autophagy agonist (Rap) and autophagy inhibitor (3-MA). The autophagosome was observed under electronic microscope. The autophagy related proteins (LC3 and Beclin1) were detected by immunofluorescence. The cell apoptosis was measured by flow cytometry. Results With 5-_{20 μmol/L}of ATO, HepG2 cells exposed to 3-MA had significantly lower viability (P <0.05) and higher early apoptosis (P <0.05) than those without exposure to 3-MA. Exposure to 3-MA was also associated with lower expressions of LC3 and Beclin1, with HepG2 cells showing typical apoptotic characteristics. By contrast, with 5-_{20 μmol/L}of ATO, the cells exposed to Rap showed significantly higher viability (P <0.05) and lower early apoptosis (P <0.05) than those without exposure to Rap. A large number of autophagosome appeared in the cells exposed to Rap. Exposure to Rap was associated with increased expressions of LC3 and Beclin1, but with no statistical significance (P >0.05). Conclusion Targeted autophagy inhibition can significantly increase the sensitivity of HepG2 to ATO. The underlining mechanism is associated with enhanced apoptosis of hepatocellular carcinoma cells.