Objective To explore the significance of the dynamic changes of cardiac stem cells after the acute myocardial infarction in rats. Methods The anterior descending coronary artery of 50 healthy adult SD rats was ligated to prepare an acute myocardial infarction model. Cardiac function indicators, including the left ventricular ejection fraction (LVEF), left ventricular shortening fraction(LVFS), left ventricular end-diastolic diameter (LVEDD), left ventricular end-diastolic volume (LVEDV) and diastolic left ventricular posterior wall thickness (LVPWT) were detected by echocardiography preoperatively and 1 week, 2 weeks, 3 weeks and 4 weeks postoperatively. The hearts of each group of rats were collected. Paraffin sections were stained with Masson to determine the pathological changes of myocardial infarction. The heart slices of all groups were immune-colored by using immunohistochemical technique and the dynamic changes in stem cell antigen-1（Sca-1）⁺ and Nanog⁺ myocardial stem cells were observed. The number of cells expressed in each group were quantitatively analyzed. The protein content of Sca-1 and Nanog was observed by Western blotting. Results The rat cardiac function began to reduce 1 week after the operation, and maintained at a relatively lower level 3 weeks later. Masson staining showed obvious scar tissue in myocardial infarction area, which confirmed the success of model preparation. The immunohistochemical result showed that the Sca-1 and Nanog positive cardiac stem cells number rose to a peak at 2 weeks and decreased afterwards. Conclusion Sca-1 and Nanog positive cardiac stem cells showed a tendency to rise first and then decrease during the pathological changes of myocardial infarction, suggesting that myocardial stem cells may play an important role in myocardial injury and repair. Masson to determine the pathological changes of myocardial infarction. The heart slices of all groups were immune-colored by using immunohistochemical technique and then the dynamic changes in stem cell antigen-1（Sca-1）⁺ and Nanog⁺ myocardial stem cells were observed. The number of cells expressed in each group was quantitatively analyzed. The protein content of Sca1 and Nanog was observed by Western blotting.  Results The rat cardiac function began to reduce 1 week after the operation, and maintained at a relatively lower level 3weeks later; Masson staining showed obvious scar tissue in myocardial infarction area, which confirmed the success of model preparation; The immunohistochemicalresult showed that the Sca1 and Nanog positive cardiac stem cells number rose to a peak at 2 weeks and decreased afterwards.  Conclusion Sca1 and Nanog positive cardiac stem cells showed a tendency to rise first and then decrease during the pathological changes of myocardial infarction, Suggesting that myocardial stem cells play an important role in myocardial injury and repair.