Immune tolerance at maternal-fetal interface is the basis for establishment and maintenance of successful pregnancy. T cells are pivotal compositions of uterine decidual immune cells, which are required to mediate anti-infection immunity and protect embryos from external antigens attack. T cells also participate in the complex immune regulation process of maternal acceptance of semi-allogeneic embryos, and play an important role in regulating embryo implantation and maintaining pregnancy. Its dysfunction may lead to early pregnancy failures or mid-late pregnancy complications. This review summarizes the compositions, phenotypic characteristics and functions of decidual T cells at the maternal-fetal interface in recent years, and further describes the regulation of decidual CD4+ and CD8+ T cells in maternal-fetal immune tolerance as well as the molecular mechanisms of abnormal regulation leading to early pregnancy failures. Through the in-depth understanding the mechanism of maternal-fetal immune regulation, it supplies a novel concept on maternal-fetal immune tolerance and new clues for the immunotherapy of pregnancy-related diseases.