Objective To investigate the role of sirtuin 2⁃related enzyme 3（SIRT3）regulating mitophagy in H2O2⁃induced apoptosis of alveolar type Ⅱ epithelial cells. Methods The mouse type Ⅱ alveolar epithelial cell line（MLE ⁃12）in logarithmic growth period was used to establish MLE ⁃ 12 cell apoptosis model with 0.5 mmol/L H2O2. The model was divided into normal control group，H2O2 injury group，H2O2+SIRT3 group，and H2O2+SIRT3 silence group. CCK8 was used to detect the proliferative activity of cells in each group；SOD，MDA and T⁃AOC kit were used to detect the level of SOD，MDA and T⁃AOC；The mRFP⁃GFP⁃LC3 autophagy double label system was constructed，and the autophagy level was observed by laser confocal microscopy；The changes of mitochondrial membrane potential and ROS level were observed by laser confocal microscopy；Western blot was used to detect the expression level of SIRT3，Bcl⁃2，Bax and LC3B. Results Compared with those in the normal controls，the level of MDA and ROS and autophagosome and autolysosomes were increased in the H2O2 injury，H2O2 + SIRT3 and H2O2 + SIRT3 silencing group（P < 0.05）. Reduced cell viability，SOD，T ⁃AOC levels，and mitochondrial membrane potential（P < 0.05），reduced protein expression of SIRT3 and Bcl2（P < 0.05），and increased Bax and LC2Ⅱ protein expression（P < 0.05）were observed，particularly significantly in the H2O2 + SIRT3 silencing group. Compared with those in the H2O2 injury group，the level of MDA and ROS and the number of autophagosome and autolysosome points were decreased in the H2O2 + SIRT3 and H2O2 + SIRT3 silencing group（P < 0.05）； increased cell viability，the level of SOD and T⁃AOC，and mitochondrial membrane potential（P < 0.05），elevated expression of SIRT3 and Bcl2 protein（P < 0.05），reduced expression of Bax and LC2Ⅱ proteins were observed （P < 0.05）. Conclusion SIRT3 can alleviate H2O2⁃induced alveolar type Ⅱ epithelial cell damage by inhibiting autophagy，oxidative stress and apoptosis.