Objectives To explore the clinical features and prognosis of patients with myasthenic crisis （MC）. Methods The general data of 74 first-time MC patients with myasthenia gravis（ MG） were reviewed for Osserman classification， time of crisis， pre-crisis characteristics， duration of the crisis， and effectiveness and prognosis evaluation of the MC treatment. Results MC patients with thymoma accounted for 60.81% of all participants， and non-thymoma patients accounted for 39.19%. 60.81%（ 45/74） of MC patients' first MC occurred within 1 year since MG onset， and 76.00%（ 38/50） of all MC cases occurred within 6 months after thymectomy accounted. Dyspnea and dysphagia（ 24/74） were the most prominent characteristics before the onset of MC， followed by thymic surgery（ 11/74）， infection（ 9/74）， and hormone-related factors（ 7/74）. Among all MCs， 45.95% are Osserman type IIB， accounting for the highest percentage across all types. The intubation time of MC patients is 15（7，30）days. 44.60%（ 33/74） of MC patients required gamma globulin and/or plasma exchange combined with methylprednisolone. The most common complication of MC was the pulmonary infection （32/74）， accounting for 43.24% of all cases. The most serious complications of repeated tracheal intubation were bronchiectasis with hemorrhage and pneumothorax. After 2-10 years of follow-up， 17 patients had multiple crises after the first MC， with a mortality rate of 9.46%（ 7/74）. Conclusions MG patients with thymoma have a higher likelihood of MC than those without thymoma. Treatment of MCis difficult and requires multiple immunosuppressive combination therapy. MC is most likely to occur until six months after thymectomy. MC complications， repeated crises， and thymoma metastasis are the leading causes of death in patients.