Abstract: Objective To explore the effect of lymphocyte immunotherapy on unexplained recurrent implantation failure and analyze its related factors. Methods One hundred and eight cases with history of embryo implantation failure who were treated with allogenic peripheral blood lymphocytes in reproductive medicine center of Shanxi Maternal and Child Health Hospital from January to December in 2016 were collected as study group, and another 6324 cases received conventional frozen embryo transfer during the same period were taken as control group. The difference in pregnancy rate and abortion rate between the two groups was analyzed, and the influence of infertility type, intima scheme and age on pregnancy outcome was also analyzed. Results The average age of the study group was(32.41±4.43) years, and it was(32.05±2.66) years in the control group, without significant difference(P> 0.05). The clinical pregnancy rates of the study group and the control group were 52.78% and 42.03%, and the abortion rates were 31.58% and 15.50%(P< 0.05, respectively). Then the study group was divided into primary infertility group and secondary infertility group, the clinical pregnancy rates of these two subgroups were 51.22% and 53.73%, and the abortion rates were 19.05% and 38.89%, without significant difference(P> 0.05); Classifying study group into hormone replacement therapy group, nature cycle group and induced ovulation group, the clinical pregnancy rates of three subgroups were 54.10%, 51.51% and 50.00%, and the abortion rates were 27.27%, 47.06% and 14.29%, without significant difference(all P> 0.05); Classifying study group into < 30 years, 30-36 years and ≥ 37 years subgroups, the clinical pregnancy rates of three subgroups were 71.96%, 50.00% and 29.41%(P for trend <0.05), and the abortion rates were 27.27%, 30.00% and 60.00%(P> 0.05). Conclusion Patients with unexplained recurrent implantation failure have a higher clinical pregnancy rate after lymphocyte immunotherapy, while they still have a higher abortion rate than patients in the control group. The clinical pregnancy rate decreases with age. Infertility type and different endometrial preparation schemes have no effect on the pregnancy outcome.