Excessive sputum after having lung surgery may be due to postoperative infection, bronchial damage, pleural effusion and other reasons. 1. Postoperative infection: Patients with profuse sputum after having lung surgery may be due to poor postoperative care or other causes of postoperative infection. Patients may experience fever, coughing up sputum, coughing and other symptoms. Some patients may experience chest pain, dyspnea, and hemoptysis. 2. Damage to the bronchial tubes: Localized damage to the trachea may occur during lung surgery, leading to bronchitis. When suffering from bronchitis, patients will cough up phlegm and other symptoms, and sometimes cause bronchospasm, shortness of breath and chest tightness. 3. Pleural effusion: after lung surgery, it may cause the patient to develop pleural effusion, which will lead to lung compression, but also stimulate the trachea, resulting in coughing and phlegm symptoms. There are other causes of phlegm after lung surgery, which should be treated promptly.