Congenital hypoplasia of the lungs can be divided into 3 categories according to the degree of its occurrence: pulmonary agenesis: one or both lungs are absent; pulmonary hypoplasia: the bronchial primordium is in a terminal blind sac and no pulmonary vessels or lung parenchyma are seen; pulmonary hypoplasia: bronchial, vascular and alveolar tissue is visible but reduced in number and/or volume. Patients may have associated pulmonary vascular and other malformed lesions. One side of the thorax collapse is one of the typical symptoms of pulmonary congenital dysplasia, so how to confirm the diagnosis of one side of the thorax collapse due to pulmonary congenital dysplasia by examination? Laboratory tests: Arterial blood gas analysis shows hypoxemia while arterial carbon dioxide partial pressure is in the normal range. Other auxiliary examinations 1, chest computed tomography (CT) scan: especially three-dimensional imaging scan can clearly show tracheobronchial malformations, angiography and color Doppler examination can help to observe the vascular (pulmonary arteries and veins) malformations, so as to identify other causes of pulmonary atelectasis and bronchiectasis. 2.Fiber bronchoscopy: It helps to observe the bronchial lumen and obstruction. 3, pulmonary function tests: pulmonary function shows restrictive ventilation dysfunction, reduced pulmonary compliance and increased airway resistance.