Whether a pleural effusion will get better without treatment needs to be determined by the amount of fluid and the specific cause. A small, unilateral, asymptomatic amount of fluid may absorb on its own, while a large amount of pleural effusion will not resolve on its own without treatment. Pleural effusion is classified according to the cause as infectious pleural effusion, tumor pleural effusion, traumatic pleural effusion, cardiogenic pleural effusion, and pleural effusion caused by connective tissue disease. A small number of pleural effusions caused by trauma may be self-absorbed and gradually recover if the amount of fluid is relatively small. If the trauma is more serious, due to persistent bleeding, active treatment is needed and it is difficult to recover on its own. Infectious cause of pleural effusion, need to actively take anti-infection treatment, otherwise it is easy to cause pleural adhesion, pus chest and other complications. Tumor, connective tissue disease, heart disease caused by pleural effusion, active treatment of the primary disease, in order to minimize the accumulation of fluid. After the appearance of pleural effusion, do not blindly expect to recover on their own, but go to the regular hospital in time, so as not to delay the condition.