Background: Coronary heart disease (CHD) caused by diabetes mellitus (DM) is the main cause of death in diabetic patients. The treatment of diabetes complicated with coronary heart disease (DM-CHD) is still a big challenge in the medical practice. Endothelial-mesenchymal transition (EndMT) has been considered as the key process in endothelial dysfunction in the atherosclerotic diseases, including DM-CHD. The traditional Chinese prescription Fufang Zhenzhu Tiaozhi (FTZ) formula is used to treat diabetes and dyslipidemia. Recently, several studies have shown the therapeutic effect of FTZ in cardiovascular diseases. However, the mechanism of the protection on coronary atherosclerosis is still needed for further investigation.Objective: To evaluate the efficacy of FTZ in preventing DM-CHD and explore the specific mechanism of FTZ based on EndMT. Methods: DM-CHD minipigs model constructed by using high-fat/high-sucrose/high-cholesterol diet (HSFCD) combined with streptozotocin (STZ) and coronary balloon injury, then randomly divided into control (Ctrl), DM-CHD model (Mod), DM-CHD treated with FTZ (FTZ) or positive drug (metformin and atorvastatin, M+A). Twenty-two weeks after administration, the cardiac functions of pigs were detected by ultrasound and electrocardiography (ECG). The stenosis and plaque of the left anterior descending (LAD) coronary artery were assessed through angiography, intravascular ultrasound (IVUS), and optical coherence tomography (OCT). Pigs were sacrificed after all examinations and the tissues were collected for further testing. The serum levels of blood glucose and lipid, myocardial injury markers, and inflammatory factors were detected. The biomarkers of EndMT were observed. The potential targets and signaling pathways were analyzed. The human umbilical vein endothelial cell (HUVEC) was cultured for testing the effect of FTZ under high glucose (HG).Results: In the Mod group, the serum levels of FBG, TC, TG, HDL-C, and LDL-C and the myocardial injury markers (LDH, cTnT, CK-MB) were increased significantly. The ST segment and the height of the T wave of ECG were significantly elevated in the Mod group. The results of coronary angiography, OCT, and IVUS showed that there was an obvious narrow in the coronary artery of the Mod group, and the pathological changes were mainly intimal fibrosis. Furthermore, the levels of TGF-β1 and α-SMA significantly increased while the levels of CD31 and VE- cadherin notably decreased in the Mod group, which showed EndMT characteristic. Besides, the inflammation and apoptosis pathways were markedly activated in the Mod group. After treatment with FTZ, the glucolipid metabolism and the myocardium injury were effectively improved in DM-CHD minipigs. FTZ treatment improved the function of the heart and alleviated coronary stenosis. The expression of α-SMA in the coronary artery was significantly decreased, and the expression of CD31 and VE-cadherin were increased in the coronary artery of the FTZ group minipigs. In addition, FTZ treatement inhibited the expressions of the inflammatory relative protein p-IκB/p-NF-κB/IL-1β and the apoptosis proteins Bax/cleave-Caspase-3 in the coronary artery tissue. Additionally, FTZ ameliorated the injury effect and high migration activity of HUVECs caused by HG. Conclusions: Coronary atherosclearosis plaque formation is related to EndMT and FTZ protect heart partly via inhibiting coronary endothelial EndMT and regulating inflammation in DM-CHD pigs.