Abstract: B7-H3 is an immune checkpoint molecule overexpressed on the surface of a variety of tumors, and is is an ideal target for tumor immunotherapy. In this study, nitrolated T cell epitope designed in the early stage of the laboratory was used to construct an epitope vaccine that can target immune checkpoint B7-H3. The vaccine can significantly inhibit tumor growth in the CT26 colon cancer model, and has a significant synergistic effect with the PD-L1 protein vaccine. B7-H3 vaccine can increase the proportion of CD4⁺ T cells in splenic T lymphocytes and the proportion of CD8⁺ T cells in tumor-infiltrating T lymphocytes, while reducing the proportion of suppressor Treg cells in tumor-infiltrating CD4⁺ T lymphocytes, which effectively improves tumor immunosuppressive microenvironment. Research results suggest that the B7-H3 epitope vaccine can be used as an effective tumor vaccine candidate molecule.