Objective:To study the polymorphism distribution of estrogen receptor (ER) α gene and the correlation between different types of polymorphism in multiple sclerosis (MS) and neuromyelitis optica (NMO) patients.Methods:Forty-six cases of MS and NMO diagnosed from June 2018 to December 2019 were collected. Peripheral venous blood samples were collected. The patient’s gender, age of onset, course of disease, and other clinical data were recorded. Fifty-eight healthy volunteers of the same age and sex were selected. By means of Pvu II and Xba I restriction fragment length polymorphism enzyme recognition sites of ER α gene, polymerase chain reaction-restriction fragment length polymorphism analysis was conducted.Results:There was no significant difference in the frequency distribution of ER α gene’s PP, Pp, and pp genotype between MS and NMO case group and control group (P = .598). Frequency distribution of ER α gene’s XX, Xx, and xx was statistically significant between MS and NMO case group and control group (P = .021). Among them, distribution of Xx and Xx gene frequency between patient group and the control group was statistically significant (P = .001, OR = 4.622, 95% CI: 1.803–11.852). There was no significant correlation between ER α genotypes and the onset age in patient group (P > .05). The difference was statistically significant in disease duration of XX and Xx genotype (P = .006). The comparison of Xx and xx genotype frequency distribution in gender exists a difference(P = .047, OR = 7.500, 95% CI: 1.023–54.996).Conclusions:Xba I gene polymorphisms in the ER α gene have correlation with MS and NMO. Xba I gene could be a risk factor of MS and NMO pathogenesis, especially the women with Xx genotype are more vulnerable. Xba I gene polymorphisms in the ER α gene may impact the disease duration of MS and NMO, or rather, the disease duration of Xx genotype persists longer than Xx genotype. Pvu II gene polymorphisms in the ER α gene has no correlation with MS and NMO.