After the early surgery of lung cancer, there will often be pleural effusion, which is a reactive effusion and is caused by pleural reaction. Therefore, if there is pleural effusion after early lung cancer surgery, dynamic follow-up observation is sufficient. Of course, there are a few cases that may be implantation metastasis of the pleura after surgery, and the extraction of pleural fluid will often reveal bloody pleural fluid, which will increase progressively and cancer cells may be found in the pleural fluid, which means that pleural metastasis has occurred after early lung cancer surgery.