CT is reviewed 1 month after surgery for thymoma, and a small fluid density shadow, i.e. pleural effusion, is seen on imaging. Generally, small thymoma will not cause pleural effusion after surgery. If the thymoma is large, it is easy to cause pleural effusion due to the large trauma caused by the need for complete resection. It may also be caused by postoperative inflammation or hypoproteinemia. Pleural effusion is a common clinical condition characterized by the accumulation of pathological fluid in the pleural cavity. If the amount of pleural effusion is relatively small, it can usually be absorbed by itself; if the amount of pleural effusion is large and the patient has already developed obvious symptoms, then pleural puncture is needed to treat it. If the image of CT examination 1 month after thymoma surgery is a little liquid density shadow, it means that the amount of pleural effusion is small, if combined with fever, cough and other symptoms, it is considered that there is inflammation, which needs to be examined and given antibiotic treatment by the doctor; if the examination of the blood protein content is low, and the effusion is caused by hypo-proteinemia, it can be given a high-protein diet, and if necessary, it can be inputted into the treatment of albumin. In addition, you can usually pay more attention to rest, work and rest, appropriate enhancement of immunity, with the doctor’s medication to relieve, prohibit spicy and stimulating food.