Coronary heart disease is the most common and frequent group of diseases. Although the level of treatment for coronary heart disease has been greatly improved by the development of interventional therapy and surgical bypass surgery, about 50% of patients can only undergo incomplete revascularization, and about 20% of patients with coronary heart disease are unable to undergo these treatments at all, and after treatment, there is often no improvement in blood perfusion at the myocardial cell level, which eventually progresses to heart failure, etc. The prognosis is extremely poor. A variety of bone marrow stem cells have been used to treat myocardial infarction in coronary artery disease with good results. Current studies have preliminarily shown that stem cell therapy for coronary heart disease may lie in mechanisms such as their differentiation into vascular endothelial cells, smooth muscle cells, cardiomyocytes, secretion of cytokines and fusion with cardiomyocytes. These findings suggest that various types of bone marrow stem cells have a role in promoting vascular neovascularization and are likely to be an effective treatment for clinical coronary heart disease and angina pectoris. Among them, bone marrow CD34+ stem cells have the function of releasing cytokines, improving vascular endothelial function, and promoting vascular neovascularization, which are the most promising types of therapeutic stem cells at present. The progress in this area is reviewed as follows: 1. The need for clinical treatment In the past 20 years, with the development and popularity of medical intervention and surgical bypass surgery for coronary artery disease, it has been able to rapidly resolve a part of coronary artery lesions with severe stenosis or even occlusion, and to a certain extent, prevent the progression of disease and sudden death in such patients. However, complete coronary artery revascularization is not possible in a significant proportion of patients, especially in those with diffuse, small-vessel and microvascular lesions throughout, and effective perfusion at the myocardial cell level is often not achieved using the methods described above [1]. Some severe lesions are not amenable to coronary intervention and surgical bypass surgery at all, or patients are unwilling to undergo intracorporeal stenting and invasive open-heart surgery, preferring only conservative pharmacological treatment, and their disease often progresses. The number of stem cells in bone marrow mononuclear cells is often less than 1%, and the effect is poor. In 2001, Orlic [2] and others published an exciting study in the journal Nature in which they injected bone marrow single nucleus cells derived from bone marrow into ligated coronary artery lesions. injected into the infarcted myocardial area of mice with ligated anterior descending branches of the coronary arteries and found that after 9 days their myocardial contractile function improved in the infarcted area and the infarct size was reduced by about 68%, thus suggesting that the transplanted stem cells were transformed into cardiomyocytes. Many similar clinical and experimental studies followed to support the myocardial repair effect of bone marrow stem cells [3-4]. However, other studies reported a completely different conclusion using genetic methods for markers – that stem cells cannot be converted into cardiomyocytes, but may be stimulated by cell fusion and secretory factors of transplanted stem cells [5-7]. Subsequently, the transformation of transplanted stem cells into cardiomyocytes and their therapeutic effects have been debated despite the publication of relevant studies [8-11]. Recently, with the continuous efforts of basic and clinical scientists from all over the world, the safety and efficacy of stem cell therapy for coronary heart disease have been confirmed. the angiogenic effect of CD34+ cells has been more clearly defined, and further research on their therapeutic mechanism and more effective specific treatment methods is needed in the future. 3, the neovascularization effect of stem cells Bone marrow stem cell transplantation was first used to treat coronary heart disease, acute myocardial infarction, and achieved good efficacy [3, 5]. It is now believed that the mechanism may be the conversion of transplanted bone marrow stem cells into cardiomyocytes; however, some scholars are skeptical about the conversion of stem cells into cardiomyocytes [6-11] and believe that the improvement of cardiac function in most patients is due to vascular neovascularization improving the remodeling of the ventricles. And the role of stem cells transformed into vascular endothelial cells and smooth muscle cells, promoting vascular neovascularization as well as releasing cytokines to regulate vasodilatory function is established and widely accepted [6-8]; due to the pro-vascular neovascularization effect of stem cells [12-13], some people have tried to treat coronary heart disease, angina pectoris with CD34+ stem cells and achieved better efficacy [14]. 4, CD34 positive stem cells become the most promising pro-angiogenic cells CD34+ stem cells are strong seed cells for improving vascular endothelium and promoting hemodynamic reconstruction, and bone marrow CD34+ stem cell transplantation is an extremely promising method for treating coronary heart disease and angina [15-17]. We ourselves used this method to treat 5 cases of coronary artery disease, and all of them achieved more obvious results. Therefore, an in-depth study of the mechanism of CD34+ stem cell transplantation for the treatment of coronary artery disease, to explore its role in promoting revascularization and reconstructing the coronary artery network, is of great significance for selecting the best indications, selecting the type of transplanted stem cells, selecting the route and site of stem cell injection, and better carrying out clinical treatment. However, the homing and revascularization effects of autologous bone marrow CD34+ stem cells after transplantation in the living state are still unclear, and it is expected that research in this area will be strengthened in the future to further elucidate their therapeutic mechanisms and lay a solid foundation for large-scale clinical treatment.