An anti-CTLA4(cytotoxic T lymphocyte associated antigen4)and anti-PD-1(programmed cell death 1)bifunctional antibody.a pharmaceutical composition thereof and use thereof.Particularly,the anti-CLTA4 and anti-PD-1 bifunctional antibody comprises afirst protein functional domain that targets PD-1 and a second protein functional domain that targets CTLA-4. The bifunctional antibody can bind to CTLA-4 and PD-1 specifically, relieve immunosuppression of CTLA4 and PD-1 on an organism specifically, activate T lymphocytes,and thus has good application prospects.