How many days to draw the pleural effusion is related to the cause of the formation of pleural effusion, the amount of effusion and the growth rate. 1. For patients with controllable and curable causes, such as infection and other causes of pleural effusion, if the pleural effusion is less than 600 milliliters, one pumping can be enough, and generally do not need to be extracted for a second time; if it is a pustular thorax, it should be pumped as much as possible at one time. 2. For patients with pleural effusion caused by malignant tumors such as lung cancer, due to the relatively large amount and fast production speed, patients often need to be extracted several times, and it is generally recommended that patients need to undergo closed pleural drainage treatment, so as to improve the discomfort symptoms and enhance the quality of life of patients. Therefore, it is recommended that if patients have any discomfort, they should go to the hospital in time to improve the color ultrasound of the relevant parts of the body, so as to clarify the cause of the disease and then provide appropriate treatment.