Pulmonary arterial hypertension (PAH) is a chronic disease that is characterized as mean pulmonary artery hypertension (mPAP) > 25 mmHg. PAH is caused by progressive obliteration of small pulmonary arteries due to known or unknown etiologies. The effect of traditional therapy is suboptimal because it can only improve symptoms but cannot cure the disease, and therefore, scientists have turned their attention to stem cell therapy for efficacious treatments. In recent years, accumulating evidences have demonstrated that endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs) are closely related with the occurrence of PAH and have the ability to prevent and reverse this disease. In this review, we turn our attention to a novel therapy for PAH, stem cell therapy, through comparing effect of preclinical research on cells and animals and evaluating the feasibility and potential difficulties of clinical application.