Objective To investigate the mechanism of early transient aggravation after glucocorticoid impact (GI) treatment in patients with myasthenia gravis (MG).Methods A total of 125 MG patients who were diagnosed and treated from January 2012 to June 2013 were selected and treated with GI. Clinical score, serum anti-acetylcholine receptor antibody (AChR-Ab) concentration, immunoglobulin IgG, complement C3, and electromyogram were analyzed before and after treatment.Results On days 7 and 28 of GI treatment, the response rates were 57.78% and 75.56%, respectively. The incidence of MG transient aggravation was 36.0%. After aggravation, patients had a significantly increased clinical absolute score (P<0.05), and the decreases in the low-frequency repeated electrical stimulation amplitudes of the radial nerve and axillary nerve were also significantly increased (P<0.05). Serum AChR-Ab, IgG, and C3 levels showed no significant changes after aggravation (P>0.05).Conclusions MG patients have a risk of early transient aggravation after the treatment of GI, which may be related to the hormone suppression of neurotransmitter transmission, but has nothing to do with the changes in antibody and complement levels.