The invention belongs to the technical field of tumor prevention and treatment and concretely relates to a Clec9a-targeting affinity peptide WH peptide and its preparation method and use. The peptide comprises 12 amino acids, has an amino acid sequence of WPRFHSSVFHTH and can be prepared through an Fmoc solid-phase synthesis method. The peptide can be used in tumor prevention and treatment. The peptide can be obtained through phage-displayed peptide library technology screening. The result of the research on an in-vivo and in-vitro foreign antigen cross presentation capacity and induction cases of specific CTL reaction shows that the WH peptide as a targeting carrier can well induce specific CTL response, improve IFN-gamma and related cell killing molecule expression quantity and improve tumor resistance. Through a computer simulated molecular docking technology, a possible docking area between the WH peptide and the Clec9a protein and action sites of the possible docking area can be researched. The peptide provides good reference and reference significance for related research.