Abstract: Pulmonary arterial hypertension(PAH) is a fatal disease characterized by a persistent elevation of pulmonary arterial pressure and persistent structural changes in small pulmonary arterioles. The main pathological feature is vascular remodeling of the pulmonary arteries. Many studies have suggested that its pathologic mechanism includes changes of various cells and several molecular signaling pathways. Recent research indicates that vascular remodeling also involves epigenetic components, resulting in the development of PAH. Various novel therapies targeting the pathological mechanism are being developed and designed to have fewer side effects and higher efficacy. This review focuses on the pathological mechanism including pathological changes, novel signaling pathways, and epigenetics as well as advances in treatment of PAH.