Objective :To investigate the telomerase activity in MG and the correlation of telomerase activity and clinic parameters of MG、the serum level of AchRab and PsmRab、the serum level of IFN-γand IL-4 in MG.  Methods: Telomerase activity were detected with polymerase chain reaction enzyme linked immunosorbent assay(PCR-ELISA) in 16 patients with MG and 16 healthy donors served as a nomal control(NC).The serum levels of AchRab、PsmRab were detected with enzyme-linked immonosorbent assay(ELISA) in MG group.The serum levels of IFN-γand IL-4 were detected with ELISA in MG group and NC group. MG group was subdivided into subgroups.  Results:(1) Telomerase activity of CD4 in MG group were significantly higer than those in NC group (p<0.05). (2) Telomerase activity were no difference in subgroups of MG groups. (3) CD4  cell and CD4 / CD8 ratio of peripheral blood T cell subsets were higher in MG group than in NC group;CD8  cell were lower in MG group than in NC group. (4) there were no difference in IgG、IgA、IgM、C4、C3 between MG group and NC group. (5) The serum levels of IL-4 were higher in MG group than in NC group; The serum levels of IFN-γwere not found in groups.(6)There was positive correlation between telomerase activity of CD4 and CD4  cell of peripheral blood T cell subsets; There was positive correlation between telomerase activity of CD4 and the clinical absolute scores. There was positive correlation between telomerase activity of CD8 and CD8  cell of peripheral blood T cell subsets; There was positive correlation between the serum levels of IL-4 and telomerase activity and the clinical absolute scores. The positive correlation was not found between