Mediastinal tumour, also known as mediastinal mass syndrome (MMS) remains an anesthetic challenge that cannot be underestimated because of its unique growth location. In particular, a large mediastinal tumor often involves cardiopulmonary functions which may lead to disastrous consequences. In this case, the patient had chronic onset and a large tumor located in the anterior mediastinum, with chest tightness and dysphagia as the main clinical manifestations. The patient had developed to massive pericardial effusion, occlusion of the right pulmonary artery in supine, oppression of 50% of the airway, and segmental atelectasis. We adopted preoperative volume reduction, sober intubation and other methods to minimize cardiopulmonary pressure, which provided benefits for general anesthesia management in tumor resection. Also we actively prevented retentive pulmonary edema after surgery, and achieved relatively stable and safe perioperative management. We hope that the experience of this case can provide reference for the perioperative management of mediastinal tumors.