To observe the short-term effects of different doses of tacrolimus (FK506) in the treatment of patients with refractory myasthenia gravis. Methods: Thirty-two patients with refractory myasthenia gravis (MG) were randomly divided into two groups: group A (2 mg/d) and group B (3 mg/d). Therapeutic efficacy was analyzed at the 2nd, 4th, and 12th week, and adverse reactions were recorded. Results: Twenty-five patients completed the trial, 11 in group A and 14 in group B. Compared with before treatment, clinical scores of MG in group A were significantly decreased at 4 and 12 weeks after treatment (P<0.05). Compared with before treatment, clinical scores in group B showed significant difference at 2, 4, and 12 weeks after treatment (P<0.05). At 2 weeks after treatment, reduction in clinical scores of group B was greater than that of group A (P<0.05). There was no significant difference between the two groups at 4 and 12 weeks (P>0.05). At 12 weeks after treatment, total effective rate of group A and group B was 81.82% and 85.71%, respectively, and the difference was not statistically significant (P>0.05). After taking FK506, a total of 6 patients experienced different degrees of systemic/joint pain, nausea, bloating, diarrhea, and other adverse reactions, all of which were improved after symptomatic treatment or withdrawal. The difference in incidence of adverse reactions between the two groups was not statistically significant (P=1.000). Conclusion: Low-dose tacrolimus in the short-term treatment of refractory myasthenia gravis can significantly improve clinical symptoms, and the incidence of adverse reactions is low.