Objective: This study aims to investigate the number changes and the clinical significance of the peripheral blood T lymphocyte subsets and NK (natural killer) cells in unexplained recurrent spontaneous abortion (URSA) patients before and after abortion, as well as after successful pregnancy. Materials and Methods: Thirty-nine URSA patients (URSA-abortion group), among who 22 patients were followed up until the final successful parturition (URSA-pregnancy group), 31 normal-pregnancy (NP) cases and 25 normal non-pregnancy (NNP) control cases in which the peripheral blood T lymphocytes and subsets, B cells, and NK cells were assessed flow cytometry. Results: Compared with the URSA-pregnancy group and the NP group, the Th cells and NK cells of the URSA-abortion group increased (p < 0.05); compared with the NNP group, the total number of T cells decreased after the first, second, and third month of the URSA abortion (p < 0.05); Th cells decreased within one to six months of the URSA abortion (p < 0.05); proportion of NK cells was significantly higher in URSA patients (p < 0.05). Conclusion: The abnormal numbers of the peripheral blood T cell subsets and NK cells were related with the occurrence of URSA.