Myasthenia gravis may be caused by poor drug efficacy, thymus tumor and so on. It is recommended that patients go to the hospital in time to improve the relevant examination and adjust the treatment program. Myasthenia gravis is an immune disease, in which 10% to 15% of patients will be accompanied by thymus tumor, about 80% of patients with thymus abnormalities. Myasthenia gravis patients who have good and bad condition during the medication may be caused by poor drug efficacy, such as the use of immune agent tacrolimus, etc., the drug dose is too small, not reached the effective dose or poor response to drug therapy, or thymus tumor. It is recommended that the patient improve the chest ct examination to clarify whether there is a tumor factor. Monitoring blood concentration, adjusting drugs, commonly used drugs are cholinesterase inhibitors, such as brompheniramine and immune agents, such as azathioprine, tacrolimus and so on. For those with significant exacerbation, plasma exchange, immunoglobulin and immunosorbent and other related treatments are feasible to alleviate the condition. If myasthenia gravis has good and bad days while taking medication, it is recommended to consult a doctor.