Purpose: To compare the post-thymectomy prognosis in different conditions of myasthenia gravis (MG) patients with thymus hyperplasia. Materials and methods: Collecting medical record and carrying out the follow-up study of 123 myasthenia gravis patients with thymus hyperplasia who have underwent thymectomy during the period between 2003 and 2013. Dividing into different groups based on gender, age of onset, duration of disease and Myasthenia Gravis Association of America (MGFA) clinical classification to analyze different prognosis in different groups. Results: Complete stable remission (CSR) was achieved in 71 of 123 patients (59.5%). There is no gender-related difference in achieving CSR. Patients with early onset of MG (40years old) or disease duration less than 12 months had significantly higher CSR rates than those with late onset of MG (>40years old) or disease duration more than 12 months respectively, while no difference was found in remission rate between MGFA clinical classification I and MGFA II. Conclusion: Myasthenia gravis patients with thymus hyperplasia who had thymectomy are proved to possess greater chance of achieving CSR. The onset age of disease and duration are the prognostic factors.