Abstract：Objective：To investigate the protective effect of astragaloside IV on rats with myocardial infarction，and to preliminarily explore its mechanism. Methods：A total of 60 model rats with myocardial infarction were prepared and randomly divided into the model group，the astragaloside IV groups with low，medium and high dose respectively and the diltiazem group，with 12 rats in each group；another 12 SD rats were selected as the sham operation group. After successful model establishment，the astragaloside IV groups with low，medium and high dose respectively as well as the diltiazem group were given the corresponding medicines by gavage at doses of 20.00，40.00，80.00 and 2.61 mg/(kg·d) respectively. The sham operation group and the model group were given the same amount of normal saline by gavage. All groups were treated for seven days. At 24 hours after the last administration， the rats were anesthetized and decapitated. In each group， the myocardial infarction areas of rats were detected by triphenyl tetrazolium chloride (TTC) staining；the levels of creatine kinase- MB (CK-MB) and cardiac troponin I (cTnI) in serum were detected by Enzyme Linked Immunosorbent Assay (ELISA)；the left ventricular function was detected by ultrasound； the changes of left ventricular end- systolic diameter (LVESD)， left ventricular end-diastolic diameter (LVEDD)，left ventricular ejection fraction (LVEF) and left ventricular fraction shortening (FS) were compared； the hemodynamics was detected； the left ventricular systolic pressure (LVSP)， left ventricular enddiastolic pressure (LVEDP)，+dp/dtmax and -dp/dtmax were compared；the expressions of PARP-1 protein in cardiac tissue of rats were detected by Western blot. Results：When compared with those in the sham operation group，the myocardial infarction areas，CK- MB，cTnI，LVEDD，LVESD，LVEDP，- dp/dtmax and expressions of PARP- 1 protein in the model group were significantly increased (P <0.05) ， and the LVEF ， FS ， LVSP and + dp/dtmax were significantly decreased (P ＜ 0.05)； when compared with those in the model group， the myocardial infarction areas， CK- MB， cTnI， LVEDD， LVESD，LVEDP，-dp/dtmax，and expressions of PARP-1 protein in the astragaloside IV groups with different doses and the diltiazem group were decreased(P＜0.05)， and the LVEF， FS， LVSP， and + dp/dtmax were increased (P＜0.05)； the astragaloside IV groups with different doses were in a dose- dependent manner(P ＜0.05). Conclusion：Astragaloside IV can down- regulate the expressions of PARP- 1 protein，reduce the myocardial infarction in model rats as well as improve the heart function and hemodynamics，so as to protect the myocardium.