Abstract: Objective：To observe the changes of memory T cells (CD4+ CD45RA- T cell) and IL-7 level in peripheral blood of patients with relapsing or nonrelapsing neuromyelitis optica, and discuss the role of memory T cells in NMO relapsing mechanism. Methods：The proportion of CD4+CD45RA- cells in the relapsing NMO group (n=15), the nonrelapsing NMO group (n=17) and the healthy control group (n=15) was detected by flow cytometry. Plasma interleukin 7 (IL-7) levels were measured by enzymelinked immunosorbent assay (ELISA) in all 3 groups. The correlation of CD4+CD45RA- cell ratio with IL-7 level in 32 patients was analyzed. Results：The CD4+CD45RA- cell ratio in the relapsing group (32.86±5.53) % was higher than that in the nonrelapsing group (19.98±5.72) % and the healthy control group (19.59±4.49) %, and the differences were statistically significant (P<0.01); the ratio in the nonrelapsing group was higher than that in the control group, but the difference was not statistically significant. The IL-7 level in the relapsing group(［418.73±78.96］ pg/mL) was higher than that in the nonrelapsing group (［313.33±57.65］ pg/mL) and the healthy control group (［303.43±40.48］ pg/mL), and the differences were statistically significant (P<0.01); the IL-7 level in the nonrelapsing group was higher than that in the healthy control group, but the difference was not statistically significant. The CD4+CD45RA- cell ratio was significantly correlated with IL-7 level in NMO patients (r=0.817, P=0.000). Conclusions：Memory T cells participate in the relapsing process of neuromyelitis optica (NMO), while IL-7 promotes the cytopoiesis and function of memory T cells.