This study aims to observe the effect of natural killer T (NKT) cell activation on experimental autoimmune myasthenia gravis (EAMG) model by injecting mice with α-GalCer in enterocoelia at different times, thus to provide a new therapy for EAMG. EAMG animal model of C57BL/6 mice was established and the mice were injected with α-GalCer irritant in enterocoelia. Vα14 NKT NKT cells were then activated through the transfer of CD1d. This paper discusses the effect of NKT cell activation on EAMG at different times by observing the variation of weight, clinical performance and relevant immunity indexes of mice. In C57BL/6 mice, the EAMG incidence rate of the Vehicle Group was 90%, the average onset duration was 37 ± 6 days; The incidence rate of α-GalCer prevention group was 30%;, the average onset duration was 51 ± 9 days. The forward immunization of α-GalCer activates NKT and protects C57BL/6 mice from the occurrence of EAMG, which provides basis for prevention and treatment of EAMG and other autoimmune diseases.