Pulmonary arterial hypertension(PAH) is a vascular disease with rapid progression, poor prognosis, and high mortality. Studies have shown that pulmonary vascular remodeling is an important pathophysiological basis for the development of PAH. The proliferation and hypertrophy of pulmonary artery smooth muscle cells are the key pathological changes of pulmonary vascular remodeling in PAH. In PAH, pulmonary vascular smooth muscle cells transformed from a contractile phenotype to a synthetic phenotype of proliferative state, mainly manifested as proliferation and hypertrophy of pulmonary vascular smooth muscle cells. These pathological changes eventually lead to vascular lumen narrow and tube wall stiffness, promoting the occurrence and development of PAH. The purpose of this review is to elaborate the mechanism of pulmonary artery smooth muscle cells in pulmonary vascular remodeling in PAH and to provide new targets and strategies for clinical prevention and treatment of PAH.