Effective diagnosis and treatment of cancer is still a great challenge to modern medicine. The advent of immunotherapy is revolutionizing the field of cancer research while drug toxicity and low responsive rates have become the most serious concerns in current treatment regimes. Dendritic cells (DCs) are the strongest antigen-presenting immune cells and play an important role in the initiation and regulation of the immune response. They can engulf a variety of foreign substances, including cell lysates and nucleic acids, and present antigens to activate the immune system. Some nanomaterials in vitro activation systems for DCs provide new ideas for immune-related therapies for tumors. Among these, magnetic nanoparticles (MNPs) have gradually become a major focus of basic scientific research and clinical treatment due to their advantages of good biocompatibility, low toxic side effects, and high ability to respond to external stimulus. The emergence of MNPs provides a novel, safe, and effective way to enhance the anti-tumor immune response. In this review, the application of MNPs as platform materials combined with DC immunotherapy is discussed, with the intention of providing a reference for future disease immunotherapy.