Pulmonary effusion is clinically known as pleural effusion, and whether it is serious or not needs to be analyzed in the context of the specific situation. If the pleural effusion is caused by pneumonia, it is usually due to pleural exudation caused by common pneumonia, which is usually not serious. If it is caused by tuberculosis, it is relatively serious, and if it is not treated, the condition will be prolonged. If it is caused by end-stage renal disease, uremia, etc., it is more serious and usually difficult to deal with. If it is caused by a malignant tumor, some patients can be controlled by radiotherapy or even targeted therapy, but most have poor treatment results and a poor prognosis. Therefore, it is recommended that patients with pulmonary effusion should go to the respiratory medicine department of the hospital for examination in a timely manner, and be judged by a professional doctor for standardized treatment and, if necessary, thoracentesis and drainage treatment.