The renin angiotensin system (RAS) has been suggested to play an important role in cardiac remodeling after acute myocardial infarction(AMI). We have confirmed that bone marrow mesenchymal stem cell-derived exosomes(BMSC-EX) had similar types of repair like effects upon tissues as bone marrow mesenchymal stem cells（BMSC),but the mechanisms remains unknown. BMSC were cultured to the third generation and were induced to release exosomes. Rats were injected with exosomes (1000µg/ml) or stem cells (1×106/ml) through the tail vein immediately after the AMI was built, compared to those treated with physiological saline. Thereafter, all groups were analyzed for cardiac function, infarction sizes, and the levels of expression of BNP, ACE, ACE2, AngII, Ang1-7, and other factors in the plasma. After H2O2 makes contact with H9C2 cardiomyocytes, cell proliferation activity and apoptotic rates were measured by using CCK8 kits,to facilitate investigation of the effect of exosomes on H9C2 cells.In vivo,the index of cardiac remodeling and cardiac function were improved in both groups of exosomes and stem cells after AMI. Furthermore, exosomes may have helped to regulate the balance of the RAS system, upregulate ACE2-Ang1-7-Mas, and downregulate the ACE-AngII-ATIR pathway. Therefore, its effects were such as to accelerate the conversion of Ang II to Ang 1-7, thereby improving cardiac remodeling and forming sustained myocardial protection. In vitro, exosomal intervention was found to have increased the levels of activity of H9C2 cardiomyocytes under H2O2 injury and improved adverse effects of AngII upon H9C2 cells.BMSC-EX improved cardiac remodeling and cardiac function, had effects upon RAS system-related factors in plasma. Similarly, BMSC-EX also helped to protect H9C2 cells under attack from H2O2 or from AngII, and may thus play beneficial roles by facilitating regulation of the balance of the RAS system.