Abstract: O bjective To observe and analyze the effect of nicotine on myocardial scar formation after acute myocardial infarction in rats and to explore its mechanism. Methods Using Lobo method to establish the model of myocardial infarction, to make the model of acut e myocardial infarction in rats, and then inject nicotine in the enterocoelia to interfere with the formation of myocardial scar; Using hematoxylin eosin (HE) staining to observe the changes of heart tissue; Using ELISA assay to measure the cardiac troponi n (cTN-T) content; Using chloramine T method to measure the content of myocardium collagen. Results Compared with control rats, the injection of nicotine in rats after myocardial infarction can result in obvious increase of serum cTN-T content, and the difference was remarkable. Conclusion Nicotine may inhibit myocardial scar formation after myocardial infarction, which may be related to the inhibition of the proliferation and differentiation of fibroblasts