This study is to investigate the role of endogenous CSE/H₂S in regulating apoptosis of HepG2 cells.  MTT and Trypan blue assay were performed to determine the effect of CSE inhibitor PAG and CSE siRNA on proliferation of HepG2.  Production of H₂S from HepG2 cells was assessed spectrophotometrically using N, N-dimethyl-p-phenylenediamine-dihydrochloride.  Cells apoptosis was detected by means of double staining of Hoechst 33342 and PI with Array Scan V^TIHCS600 High-Contents.  Dihydroethidine (DHE) and 2', 7'-dichlorodihydrofluorescein diacetate (DCFH-DA) assay was used to determine intracellular superoxide anion and ROS level.  Reduced glutathione (GSH) was determined by OxiSelect™ Total Glutathione Assay Kit.  Recombinant plasmid pcDNA 3.1/myc-His(−)-CSE was constructed and transfected into 293T cells to rescue the ROS and GSH level to further investigate the effect of CSE/H₂S on ROS and GSH.  Western blotting was performed to test the effect of CSE siRNA on expression of activated caspase 3 and p-AKT and Nrf2 protein.  The results showed that PAG and CSE siRNA could significantly decrease the production of H₂S in HepG2 cells and inhibit the proliferation of HepG2 cells at a dose-dependent and time-dependent manner, respectively.  PAG and CSE siRNA could promote the cell apoptosis of HepG2 cells.  Moreover, PAG and CSE siRNA induced increased ROS generation and depletion of the critical antioxidant GSH and recombinant plasmid pcDNA 3.1/myc-His(−)-CSE rescued the level of ROS and GSH.  Meanwhile, CSE siRNA increased the expression of activated caspase 3, but CSE siRNA did not affect the expression of p-AKT and Nrf2.  These results suggested that the CSE/H₂S pathway was involved in suppression of HepG2 cell growth and promoted apoptosis of HepG2 cells in an oxidative stress-dependent manner.