The mechanism of development of thymomas associated with myasthenia gravis(MG) is not completely clear. It is not hard to make diagnosis of thymomas associated with MG via clinical manifestation,radiological investigation and laboratory examination, however, the treatment of thymomas associated with MG remains controversial and there is no straightforward guidelines in the literatures. Most scholars think surgery is the first choice to treat thymomas associated with MG, but for those who are not suitable for surgery, radiotherapy and chemotherapy would be considered to be their choice combined with anti-cholinesterase and steroidsdrugs therapy.