A small amount of pleural effusion without underlying disease can be self-resolving, while a medium to large amount of pleural effusion with underlying disease is less likely to be self-resolving. If the pleural effusion is less than 500 ml after chest imaging, it can be defined as a small amount of pleural effusion without the combination of underlying lung diseases, then it can be absorbed on its own, and it is enough to pay attention to the changes of one’s own symptoms, and to review the symptoms in a timely manner. However, if the pleural effusion is medium to large in volume, i.e. the pleural effusion is more than 500ml, or combined with underlying lung diseases such as lung cancer, then the possibility of self-absorption is smaller, and need to be treated in time, such as for the treatment of the primary pathology, the specific selection of medication and treatment program based on the doctor’s instructions. It is recommended that patients with pleural effusion should go to regular hospitals in time and consult professional doctors.