Due to the insidious clinical presentation, most children with pulmonary hypertension are critically ill at the time of diagnosis. Although the application of various targeted drugs has improved symptoms and short-term prognosis in recent years, maintaining long-term survival and normal growth and development in children is still a difficult goal to achieve. Previous national and international studies have concluded that pulmonary hypertension in children is mainly associated with congenital heart disease, followed by idiopathic pulmonary hypertension for which no cause can be found. In recent years, we have discovered in our clinical work that, in addition to the common cause of congenital heart disease, the causes of pulmonary hypertension in children are very broad, and some of them are even previously unrecognized, such as certain genetic metabolic diseases, etc. Some of these diseases can be treated, and thus pulmonary hypertension can be treated with good results or even cured. It is becoming increasingly evident that the diagnosis and treatment of the cause of pulmonary hypertension in children is crucial, and that some clinically diagnosed idiopathic pulmonary hypertension may not be truly idiopathic, but the cause has not yet been identified. The fact that the etiology is found but difficult to treat has improved our understanding of this difficult to treat disease and has also motivated us to conduct intensive research on this disease. In clinical practice, many diseases associated with pulmonary hypertension are insidious and often not easily recognized. The detection of the cause of pulmonary hypertension requires a more extensive and comprehensive experience of pediatric cardiovascular physicians in the diagnosis and treatment of multisystem diseases in children of different ages, who are able to detect traces of the disease and perform targeted ancillary tests before the cause can be clarified, and screening by just a few routine tests and examinations is It is far from enough. In conclusion, careful investigation of the disease in children with unexplained pulmonary hypertension and treatment of the cause will undoubtedly improve the outcome of treatment of pulmonary hypertension in children and thus improve the long-term prognosis.