Abstract: The present invention relates to the field of therapeutic monoclonal antibodies, and specifically provides an anti-FXI/FXIa antibody or an antigen-binding fragment thereof, nucleic acid molecules encoding same, and methods for preparing same. The anti-FXI/FXIa antibody or antigen-binding fragment thereof described in the present invention has specificity and high affinity to FXI/FXIa, and can effectively inhibit the activity of FXI/FXIa. Therefore, the present invention further provides a pharmaceutical composition comprising the antibody or antigen-binding fragment thereof, and a use thereof in the preparation of a drug which is used for the prevention and/or treatment of diseases or disorders related to coagulation or thromboembolism.