The invention discloses application of lysophosphatidic acid, a lysophosphatidic acid receptor 3 and a lysophosphatidic acid receptor 3 agonist and relates to the field of biomedicine. The study findsout that lysophosphatidic acid or the lysophosphatidic acid receptor 3 or the lysophosphatidic acid receptor 3 agonist can promote cardiomyocyte proliferation and inhibit cardiomyocyte apoptosis to repair damaged myocardia, significantly reduce myocardial infarct areas and significantly improve cardiac functions after myocardial infarction, and the effect is obvious. Therefore, lysophosphatidic acid, the lysophosphatidic acid receptor 3 and the lysophosphatidic acid receptor 3 agonist can be used in the field of preparation of medicine, preparations and the like for treating or preventing heart diseases, and new medicine and a new treatment idea are provided for treating or preventing heart diseases such as ischemic heart disease.