Stem cell therapy has become a promising method for many diseases, including ischemic heart disease and heart failure. Several kinds of stem cells have been studied for heart diseases. Of them, bone marrow stem cells (BMSCs), which have been used in many clinical trials, are the most understood one. But the effect of BMSCs is mediated by paracrine factors instead of direct turning into cardiomyocytes. On the other hand, a lot of evidences have shown that resident cardiac stem cells could turn into cardiomyocytes directly in vivo. Currently, seven kinds of resident cardiac stem cells have been discovered. However, their mechanisms, development origins, and relationships have yet to be fully understood. Moreover, two Phase I clinical trials have been performed recently. They show promising results. In this review, we will summarize the current research on these cardiac stem cells and the methods to enhance their effects in clinical applications.