Objective To explore the diagnosis, surgical treatment and prognosis of thymoma complicated with myasthenia gravis(MG). Methods A retrospective analysis was performed in 33 thymoma patients with MG, who underwent surgical treatment. Results The total effective rate of operation was 75.8%, and the 5 and 10 years survival rates of the patients after operation were 85% and 78.7%, respectively. According to the Masaoka staging system, the 5 and 10 years survival rates of stages I and II were obviously higher than those of stages III and IV (P