Abstract: Regulatory T lymphocytes（Treg） play an important role in immune balance and immune regulation. Foxp3 is a symbolic molecule of regulatory T cells. Treg is considered to take part in tumor immune escape in host immune system， and is associated with poor survival outcome in a variety of cancers. Cytotoxic T lymphocyteassociated antigen4（CTLA-4） is expressed on activated T cells， and has negative control response in T cell immune response. CTLA-4 can also exist in organism circulation as a soluble form（sCTLA-4）， and is involved in immunological homeostatic control. CTLA-4 and Treg overlap in functions， and affect the immune regulation process together， but the mechanism of interaction is an area for further study.