Regulatory T cells are a subgroup of T cells with immunomodulatory functions. Different from most cytotoxic T cells and helper T cells, they play a supporting role in the immune system. What’s more, regulatory T cells often play an immunosuppressive role, which mainly plays a role in maintaining the stability of the immune system and regulating the immune response in the body. However, recent studies have shown that not only playing a role in autoimmune diseases, organ transplantation, and other aspects, regulatory T cells can also play a role in the immune escape of tumors in the body, through various mechanisms to help tumor cells escape from the demic immune system, weakening the anti-cancer effect in the body. For a better understanding of the role that regulatory T cells can play in cancer, and to be able to use regulatory T cells for tumor immunotherapy more quickly. This review focuses on the research progress of various mechanisms of regulatory T cells in the tumor environment, the related research of tumor cells acting on regulatory T cells, and the existing various therapeutic methods acting on regulatory T cells. •Unlike in the past, Treg cells have also been found to play a powerful role in cancer treatment.•Treg cells exert immunosuppressive effects through various ways, such as cell-cell contact, secretion of cytokines, regulation of DC function, binding to chemokine CCL22/CCL17, and so on, and acting in the tumor microenvironment.•Tumorigenesis is often accompanied by an increase in the number of Treg cells.•Many recent studies have found that metabolic pathways, receptors, and proteins on Treg cells, bile acids, and even apoptotic Treg cells can promote Treg cells to exert immune suppression, and then help tumors escape from the immune system.•More and more targeted therapy drugs that block the target sites on Treg cells and destroy the homeostasis between Th17 cells and Treg cells can be effective immunotherapy for tumors.