Abstract: Objective：To construct rat acute myocardial infarction (AMI) model and explore the repairing effect of human umbilical cord mesenchymal stem cells (hucMSCs) on the damage of AMI. Methods：In cooperation with the small animal ventilator, the rat AMI model was established by opening anocelia, extruding heart, ligating the left anterior descending coronary artery quickly and accurately, and finally closing chest combined with tightening the double purse. Next, the model was verified by using electrocardiogram, echocardiogram and TTC staining. Thereafter, hucMSCs were injected into the model rat by vena caudalis to observe their repairing effect on the damage of AMI. Results：The rat AMI models with high survival rate (79.2%) were constructed successfully. In comparison with the PBS group, the left ventricular systolic volume ［LV Vol; s (μL): 116.08 ± 9.06 vs 164.73±15.54］ and left ventricular systolic diameter ［LVID; s (mm): 4.96±0.17 vs 5.77±0.23］ in the MSCs group were significantly reduced ( F LV Vol; s=75.10, FLVID; s=107.96; P< 0.01). Meanwhile, the left ventricular ejection fraction ［LVEF(%): 53.99±2.32］ and left ventricular systolic fraction ［LVFS(%): 28.76±1.52］ in the MSCs group were significantly higher than that in the PBS group ［LVEF(%): 45.55±3.71; LVFS(%): 23.56±2.38］ (FLVEF=65.80, FLVFS=62.94; P<0.05). HE staining results of the myocardial tissue showed that the extent of cell damage in the MSCs group was obviously weaker than that in the PBS group. Conclusion：The rat AMI model was successfully constructed, and hucMSCs may promote the repair of the rat AMI damage, which lays a foundation for further investigating their mechanism of action.