• 1\. Age ≥18 and gender unlimited；

• 2\. Confirmed as refractory myasthenia gravis with AchR antibody positive and accord one of the following three conditions

‣ Repeated electrical stimulation suggests neuromuscular conduction deficits；

⁃ Tensilon test and neostigmine test positive;

⁃ The doctor judged that the symptoms of MG improved after treatment with oral cholinease inhibitors;

• 3\. Consistent with the clinical classification of MGFA myasthenia gravis IIa-IVb (including IIa，IIb，IIIa， IIIb， IVa，IVb)

• 4\. The baseline MG-ADL score ≥5 and the musculi oculi related score\< 50 ；

• 5\. Baseline QMG score\>11;

• 6\. Regular treatment with poor efficacy and/or lack of effective treatment means that there is still recurrence or exacerbation after treatment with conventional hormones, immunosuppressants (such as azathioprine, mycophenolate mofetil, tacrolimus, cyclosporine A, cyclophosphamide, etc.) or rituximab；

• 7\. The estimated survival time is more than 12 weeks;

• 8\. Women of childbearing age who have negative urine pregnancy test before medication administration and agree to take effective contraceptive measures during the trial period until the last follow-up.