Surgery plays an important role in the treatment of anterior mediastinum disease. The major surgical approaches include: cervical approach, mid-sternal approach, cervical combined mid-sternal approach and video-assisted thoracoscopic approach. The cervical approach is rarely adopted because of its restricted visual field. The cervical combined mid-sternal approach have a broader field of vision, given this advantage, the surgeon can remove the thymus and its surrounding fat tissue more thoroughly. But the trauma of this approach is much larger, and the postoperative complication is also a serious problem. The video-assisted thoracoscope is often adopted by left or right approach, this minimally invasive procedure can not remove anterior mediastinum fat thoroughly. In clinical practice, the investigators designed a new method named "3-Hole" subxiphoid approach. This study is designed to compare the safety and validity between this new method and others.

Inclusion Criteria:

• MG with thymic hyperplasia, thymoma or other anterior mediastinum disease
• Masaoka stagingⅠ-Ⅱ
• Thymoma without MG
• Mass diameter <10cm
• Inform Consent Form is signed

Exclusion Criteria:

• Unable to tolerate surgery
• myasthenic crisis
• Masaoka staging Ⅲ-Ⅳ
• Patients who have undergone previous surgery or radiotherapy
• pregnancy , breastfeeding or younger than 18 years old