Whether pulmonary effusion in the elderly is dangerous or not needs to be judged according to the cause of pulmonary effusion in the elderly. Need to actively treat organ failure, usually also irreversible and very dangerous; 3, pleural effusion caused by simple infection, if it is tuberculous pleural effusion, need to be treated for a year to a year and a half, ordinary lung infection caused by pleural effusion need anti-infective treatment; 4, malnutrition or hypoproteinemia caused by pleural effusion, need to supplement nutrition. The prognosis for pleural effusion caused by these three causes of infection, malnutrition or hypoproteinemia is relatively good if there are no serious complications.