Increased affinities mainly equals to improved biological efficacy in many cases.By now display methods including phage library are widely exploited to obtain higher affinity antibodies.Traditional library methods mainly focus on CDR mutagenesis, in which extensive screening of variant combinations as well as large library capacity is required to find higher affinity clones.In this study, based on the modeling 3-D complex structure of antigen (Her2)-antibody (MIL5) complex, the key residues of contact surface were predicted and identified to guide the synthetic phage library design.Then, epitope-specific phage library which was comprised of MIL5_scFv mutants was constructed, and according to our design, all mutants identified similar epitope to parent antibody.Ultimately, a higher affinity single chain antibody (M5scFv_ph) was screened out from the library.Following experimental results showed that the novel antibody M5scFv_ph retained superimposed epitope to the parent antibody MIL5_scFv, and possessed similar tumor growth inhibitory activity in vivo on ovarian carcinoma xenografts, which was consistent to the theoretical results.