Background: Neuromyelitis optica (NMO) and multiple sclerosis (MS) are autoimmune demyelinating diseases of the central nerve system.Interleukin-7 (IL-7) and interleukin-7 receptor alpha (IL-7Rα) were proved to be important in the pathogenesis of both diseases because of the roles they played in the differentiations of autoimmune lymphocytes.The variants of both genes had been identified to be associated with MS susceptibility in Caucasian, Japanese and Korean populations.However, the association of these variants with NMO and MS has not been well studied in Chinese Southeast Han population.Here, we aimed to evaluate the association of six IL-7 variants (rs 1520333, rs1545298, rs4739140, rs6993386, rs7816065, and rs2887502) and one variant of IL-7RA (rs6897932) with NMO and MS among Chinese Han population in southeastem China.Methods: Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MassARRAY system) and Sanger sequencing were used to determine the variants ofIL-7 and IL-7RA in 167 NMO patients, 159 MS patients and 479 healthy controls among Chinese Han population in southeast China.Samples were excluded if the genotyping success rate ＜90％.Results: Statistical differences were observed in the genotypes ofIL-7 rs 1520333 in MS patients and IL-7RA rs6897932 in NMO patients,compared with healthy controls (P =0.035 and 0.034, respectively).There was a statistically significant difference in the genotypes of IL-7 rs2887502 between MS and NMO patients (P =0.014).And there were statistically significant differences in the rs6897932 genotypes (P =0.004) and alleles (P =0.042) between NMO-IgG positive patients and healthy controls.Conclusions: The study suggested that among Chinese Han population in southeast China, the variant of IL-7RA (rs6897932) was associated with NMO especially NMO-IgG positive patients while the variant of IL-7 (rs1520333) with MS patients.And the genotypic differences ofIL-7 rs2887502 between MS and NMO indicated the different genetic backgrounds of these two diseases.