Abstract: The present disclosure relates to an immunologically active peptide-biliverdin conjugate (I), a preparation method therefor and an application thereof in cancer diagnosis, and/or tumor immunotherapy, and/or tumor “photothermal immunotherapy” (tumor photothermal therapy combined with immunotherapy). The conjugate to which the present disclosure relates not only may stimulate an organism to generate a tumor-immune effect, but also may relieve and/or eliminate tumor inflammation, remodel a tumor inflammatory microenvironment and achieve photothermal cancer immunodiagnosis and immunotherapy. The conjugate to which the present disclosure relates has high biocompatibility, good stability and an extended half-life. The conjugate is prepared from an immunologically active peptide and biliverdin by means of chemical synthesis.