Left lower lobe atelectasis is a solid change in the left lower lobe of the lung with reduced volume as suggested by chest CT. It is necessary to exclude whether it is caused by bronchial pathology, including tuberculosis, bronchial tuberculosis, bronchial foreign body, sputum obstruction, or lung tumor. After CT of the chest suggests pulmonary atelectasis, further microscopic examination by fiberoptic bronchoscopy needs to be given to find out whether there are foreign bodies, sputum, tumors, or even tuberculosis-like changes in the bronchi. If tuberculosis-like caseous changes are present, standardized anti-tuberculosis treatment and bronchial balloon dilatation are indicated. In the case of tumor-like lesions, cellular tissue biopsy can be taken to determine whether the tumor can be treated with early surgical resection. In the case of atelectasis caused by foreign body obstruction in the bronchi of the respiratory tract, the foreign body should be removed to restore the atelectasis. If it is caused by sputum clots or sputum, microscopic aspiration should be given to promote early reopening of the lung. In addition to congenital pulmonary dysplasia, inflammation, foreign body, tuberculosis, and tumor are the main factors to be considered in left lower lung dysplasia.