OBJECTIVE：To study the imp rovement effects of Polygonatum si biricum polysaccharides（PSP）on the myocardial injury of acute myocardial infarction （AMI）model rats. METHODS ：The rats were randomly divided into blank control group ， model group ，aspirin group （positive control ，25 mg/kg），PSP low-dose ，medium-dose and high-dose groups （0.5，1，2 g/kg）， with 10 rats in each group. Except for blank control group ，AMI model was established by ligation of the anterior descending branch of the left coronary artery of rats in other groups. After modeling ，blank control group and model group were given normal saline intragastrically ，and administration groups were given relevant medicine intragastrically ，once a day ，for consecutive 28 days. After last medication ，left ventricular ejection fraction （LVEF）and left ventricular short axis shorting rate （LVFS）of rats were detected. The morphological changes of myocardial tissue were observed. The levels of oxidative stress indexes （SOD，MDA， ROS）in myocardial tissue of rats were detected by ELISA. The expression of apoptosis-related proteins （Bcl-2，Bax，caspase-3， caspase-8，caspase-9）and the Wnt/ β-catenin pathway-related proteins （Wnt1，β-catenin）in left ventricular anterior wall tissue of rats were detected by Western blot assay. RESULTS ：Compared with model group ，the levels of LVEF and LVFS ，the levels of SOD in myocardial tissue and protein expression of Bcl- 2 in left ventricular anterior wall tissue were increased significantly in PSP medium-dose，high-dose groups and aspirin group （P＜0.05）；the levels of MDA and ROS in myocardial tissue ，the protein expression of Bax ，caspase-3，caspase-8，caspase-9，Wnt1 and β-catenin in left ventricular anterior wall tissue were decreased significantly（P＜0.05）；myocardial tissue structure disorder and inflammatory cell infiltration were reduced. CONCLUSIONS ： PSP can relieve myocardial injury in AMI model rats ；its mechanism may be related to increasing SOD level in myocardial tissue ，decreasing MDA and ROS level ，regulating apoptosis-related proteins and Wnt/ β-catenin pathway-related proteins.