Immunogenicity of murine antibody variable regions originates with the surface residues.In order to eliminating the immunogenicity in human,humanization of the single chain Fv fragment of murine antibody against human fibrin which cloned by the phage display in the lab,was designed by resurfacing the molecule.First,the surface residues of the Fv which may induced the immunogenicity were determined.Then the differences between the surface residues of murine and human antibody Fv fragments were analyzed,and the different surface residues of the murine antibody Fv against human fibrin studied in the paper were replaced by those from human.In the study,two humanization strategies,the most similar chain surface humanization and the most frequent surface humanization,were reported.Both of the three dimensional structures of the humanized murine Fv fragment designed by the two strategies were proved reasonable by Profiles 3D program.The analyses showed that the solution accessible propertises of the mutated surface residues of the humanized Fv fragment were not changed.In addition,the CDRs structures of the two humanized Fv were not affected by the residue change,so the affinity for fibrin of them may not be declined.