Lymphocyte ⁃activation gene 3（LAG ⁃3），also known as CD223，is a transmembrane protein found on activated T cells. It can be found on the activated CD4 + T and CD8 +T，as well as on Treg，NK cells，B cells and DC. LAG ⁃3 consists of three parts：the extracellular region，penetrating region and intracellular region. Fibrinogen like protein 1，FGL⁃1，as a newly discovered ligand of LAG⁃3，which can inhibit T cell function in a receptor⁃ligand interdependent manner in vitro and in vivo. We review the role of FGL⁃1⁃LAG⁃3 pathway in tumor immunity，and aim to reveal the role of LAG⁃3⁃FGL⁃1 pathway in tumor immunity and to provide new ideas for tumor immunotherapy.