An anti-PDl (programmed cell death 1) monoclonal antibody or an antigen-binding fragment thereof, a pharmaceutical composition thereof and use thereof. The heavy chain variable region of the monoclonal antibody comprises CDRs (complementary determining region) of amino acid sequences as shown in SEQ ID NO:9-11; and/or the light chain variable region of the monoclonal antibody comprises CDRs of amino acid sequences as shown in SEQ ID NO: 12-14. The monoclonal antibody can bind to PDl specifically, relieve immunosuppression of PDl on an organism specifically and activate T lymphocytes.