Abstract: Immunotherapy has become another effective tumor treatment after surgical resection, chemotherapy, radiotherapy and targeted therapy. However, due to the low immunogenicity of tumor cells and immunosuppressive tumor microenvironment, antigen-presenting cells inefficiently process and present tumor antigens, thus leading to insufficient activation of cytotoxic T lymphocytes and tumor infiltration, which significantly affects the effectiveness of tumor immunotherapy. In recent years, it has been demonstrated that multiple metal ions exhibit distinguished modulatory effects in activating innate immune stimulation and conquering acquired immune tolerance. Based on this, scientists have designed a series of nano-adjuvant delivery systems with metal ions or metal nanoparticles to enhance the targeted accumulation of metal ions in tumor tissues or lymphoid organs for efficiently inducing immunogenic cell death or directly activating antigen-presenting cells to initiate anti-tumor specific immune response. This review briefly outlines the role of various metal ions in anti-tumor immunomodulation, summarizes the research progress in using metal nanoadjuvant delivery systems to achieve efficient anti-tumor immunotherapy, and provides foresight on the main challenges and potential directions in this field.