Cardiopulmonary exercise testing (CPET) allows for the analysis of gas exchange at rest, during exercise, and during recovery. These data can be readily integrated with standard variables measured during exercise testing, including heart rate, blood pressure, work rate, electrocardiography findings, and symptoms, to provide a comprehensive assessment of exercise tolerance and exercise responses. CPET can even be performed with adjunctive imaging modalities for additional diagnostic assessment. This paper focused on the progress in the application of CPET in the early diagnosis and prognostic evaluation of pulmonary hypertension.