Aim To investigate the role of endogenous sulfur dioxide (SO₂) in inhibiting cardiomyocyte autophagy in angiotensin Ⅱ (AngⅡ)-induced myocardial hypertrophic mice. Methods 16 healthy 9-week-old C57BL mice were randomly divided into wild type control group (WT Con group) and wild type＋AngⅡ group (WT AngⅡ group); 16 cardiac-specific aspartate aminotransferase 2 (AAT2) transgenic mice were randomly divided into AAT2 control group (AAT2 Con group) and AAT2＋AngⅡ group (AAT2 AngⅡ group); 8 mice in each group. The mouse was subcutaneously implanted with a capsule osmotic pressure pump pre-filled with normal saline or AngⅡ in the back for continuous administration for 4 weeks. Total heart weight/body weight (HW/BW) ratio was detected in 4 groups of mice. HE staining was used to observe the changes of myocardial cell structure. The expression of α-myosin heavy chain (α-MHC) was detected by immunohistochemistry staining. The content of SO₂ in myocardial tissue was detected by high performance liquid chromatography. Western blot was used to detect the expressions of endogenous SO₂ producing enzymes AAT1 and AAT2, cardiomyocyte phenotypic markers α-MHC and β-MHC as well as myocardial autophagy indicators Beclin-1, LC3, Atg4B and p62. Results Compared with WT Con group, the SO₂ content was significantly reduced (P＜0.01) but the expression of AAT1 protein had no obvious changes (P＞0.05), the expression of AAT2 protein was significantly decreased (P＜0.05), in the myocardial tissue of the mice in WT AngⅡ group; HW/BW was increased significantly (P＜0.01), and myocardial fibers were thickened; Immunohistochemistry showed that the expression of α-MHC protein was decreased in cardiomyocyte cytoplasm; Western blot results showed that the expression of α-MHC protein in cardiomyocytes was significantly decreased (P＜0.01), the expression of β-MHC protein was significantly increased (P＜0.01), and cardiomyocyte autophagy was significantly increased which was demonstrated by the fact that the ratio of LC3Ⅱ/LC3Ⅰ was significantly increased, the expressions of Beclin-1 and Atg4B protein were significantly increased, and the expression of p62 protein was significantly reduced (all P＜0.01). However, compared with WT Con group, the SO₂ content and AAT2 protein expression in AAT2 AngⅡ group were significantly increased (P＜0.01), AAT1 protein expression did not significantly change (P＞0.05), and the HW/BW ratio was significantly decreased (P＜0.05); The thickness of myocardial fibers was significantly reversed; The conversion of α-MHC protein to β-MHC protein was significantly reduced (P＜0.01), and the level of autophagy was significantly reduced in cardiomyocytes. Conclusion Endogenous SO₂/AAT2 system can inhibit the cardiomyocyte autophagy and myocardial hypertrophy in the AngⅡ-treated mice.