It takes about 2 weeks for pleural effusion caused by pneumonia to disappear after active treatment. In general, the absorption time of pleural effusion needs to be judged according to the type of pneumonia, the severity of clinical symptoms, the amount of pleural effusion and whether it has been treated in a standardized way. Generally speaking, in the case of pleural effusion caused by common lobar pneumonia, the lung inflammation and pleural effusion can be completely absorbed after about 2 weeks of active anti-infection treatment. However, when the symptoms of pneumonia are more severe, producing a large amount of pleural effusion or even pyothorax, the patient’s chest infection is more serious, and it takes more time to fully recover, and it also needs to be treated with thoracocentesis and drainage, thoracic cavity irrigation, etc., and the treatment time often takes more than 3 weeks. Pneumonia pleural effusion patients are advised to seek medical treatment in time to avoid delays.