Objective: To develop an effective therapy for myasthenia gravis (MG) with little traumatic injury and low morCT-guided percutaneous thymus paracentesis via the upper margin of the stum incisure and with local dexamethasone injection. Results: The symptoms and signs were relieved within 3 d of treatment in all the 13 MG patients; three had immediate response to the treatment with improved myodynamia. A 3-year follow-up study showed that the symptoms and signs improved significantly in 10 patients and ted for the better in 3. The size of the thymus reduced vertically, transversely and anteroposteriorly by 24.2%, 31.7% and 34.1% respectively. Low-density areas were seen in the thymus due to water gasification and coagulation necrosis of the thymus tissue. Conclusion: The technique has definite therapeutic effect on MG with advantages of easy manipulation, quick response and low morbidity. It is suitable for MG patients with hyperplasia or thymoma, and those who are unwilling to receive thymectomy, or whose thymoma is not resectable, or those who have poor response to radiotherapy.