The present invention relates to combination use of anti-PD-1 antibody or its antigen-binding fragments and IDO inhibitor in the preparation of a medicament for the treatment of tumor. The composition of anti-PD-1 antibody or its antigen-binding fragments and IDO inhibitor can effectively resolve tumor heterogeneity, play a significant role in inhibiting tumor cells, and effectively inhibit the proliferation, migration or invasion of tumor cells.本發明涉及PD-1抗體或其抗原結合片段與IDO抑制劑聯合在製備抗腫瘤的藥物中的用途。PD-1抗體或其抗原結合片段與IDO抑制劑組成物可以有效解決腫瘤異質性,發揮顯著的抑制腫瘤細胞作用,有效抑制腫瘤細胞的增殖、遷移或侵襲。