Pulmonary hypertension due to left heart disease (PH-LHD) is the most common in various types of pulmonary hypertension. Although there are many treatments for pulmonary hypertension, it may be harmful when we adopt treatment without detrimental diagnosis and classification of pulmonary hypertension. Therefore, it is very crucial to have accurate diagnosis and classification of pulmonary hypertension before making treatment decisions. However, there are still some difficulties in the classification of pulmonary hypertension in clinical work. It is a great challenge with limited treatment to solve the PH-LHD which often has complicated pathophysiological mechanisms of precapillary and postcapillary pulmonary hypertension. Here, we review the research status of PH-LHD.