Abstract: B and T lymphocyte attenuator（BTLA），a new inhibitory receptor of the CD28 family，attracts more and more attention recently after the negative co-stimulator programmed cell death molecule-1（PD-1） and cytotoxic T cell associated antigen-4（CTLA-4） discovered. The expression spectrum of BTLA is situated between PD-1 and CTLA-4. It expresses not only in T cells，but also in B cells， NK cells，macrophages and dendritic cells.It mediates inhibitory signals to T cells when binding its ligand.It is suggested that BTLA signaling pathway might play a negative regulatory role in the antitumor immune response and associate with tumor immune escape mechanism.So it is likely to become a potential target of tumor biotherapy.