Objective To investigate the effects of microRNA (miR)-145 delivered by exosomes (Exo) on platelet activation and vascular endothelial function in rats with coronary atherosclerotic heart disease (CAHD).  Methods   HEK239 cells were transfected with miR-negative control(NC) and miR-145, and the transfection effect was detected by Realtime PCR. Exo was isolated from HEK239 cells transfected with miRNA-NC and miR-145. The morphology and size distribution were observed by transmission electron microscopy. The expressions of CD81, heat shock protein 70（HSP70）and tumor susceptibility gene 101（TSG101）were detected by Western blotting. The experiment included control group, model group, miR-NC Exo group and miR-145 Exo group, with 8 rats in each group. After treatment, the ejection fraction (EF), fractional shortening rate (FS), left ventricular enddiastolic diameter (LVIDD) and left ventricular end-systolic diameter (LVIDS) of rats were determined by ultrasonic diagnostic instrument. HE staining was performed to observe the pathological changes of myocardial tissue and aortic tissue, and ELISA was used to determine serum platelet activating factor (PAF), β-platelet globulin (β-TG), platelet membrane glycoprotein Ⅱa/Ⅲb (GPⅡa/Ⅲb), nitric oxide (NO), endothelin-1 (ET-1) and vascular endothelial growth factor (VEGF). Immunohistochemical staining was used to detect the expression of endothelial nitric oxide synthase (eNOS) in aorta tissue.  Results  The relative expression level of miR-145 in HEK239 cells transfected with miR-145 was significantly higher than that in untransfected and transfected miR-NC cells (P <0.05). The isolated particles showed typical cup-shaped or disk-shaped vesicles, most of which were distributed at 100 nm in diameter. CD81, HSP70 and TSG101 proteins were highly expressed, and the relative expression level of miR-145 in Exo transfected with miR-NC was significantly lower than that in Exo transfected with miR-145 (P <0.05). Compared with the miR-NC Exo group, EF and FS of miR-145 Exo group increased significantly(P <0.05), while LVIDD and LVIDS decreased significantly(P <0.05), and the pathological changes of myocardial tissue and aortic tissue were better improved. The contents of PAF, β-TG, GPⅡa/Ⅲb, ET-1 and VEGF in serum were further significantly decreased (P <0.05), while the content of NO was also significantly increased (P <0.05), and the positive expression rate of eNOS in aortic tissue was further significantly increased (P <0.05).  Conclusion  MiR-145 delivered by Exo could inhibit platelet activation and improve vascular endothelial function in coronary heart disease model rats, and plays a protective role in coronary heart disease model rats.