Abstract: The present invention provides a use of IFN-? in preparing an anti-tumor adjuvant drug, wherein the IFN-? enhances killing effect of the T cell preparation on tumor cell by sensitizing the tumor cell; the T cell preparation comprises non-genetically engineered T cell and/or genetically engineered T cell; and the IFN-? comprises full-length or fragment of wild-type or mutant IFN-?. The present invention revises the current understanding of IFN-? in the prior art and finds that the IFN-? inhibits the acquired immune resistance mediated by PD-L1-PD-1 and enhances the anti-tumor effect of immunotherapy by activating the IFN-? signaling pathway in tumor cell.