Abstract: As a natural drug delivery system, exosomes have the advantages of low immunogenicity and natural targeting in the process of mediating tumor immunotherapy. The complex contents of exosomes from different sources determine the diversity of their functions.They participate in the transfer of materials and information among cells in tumor immunotherapy and play such important roles as presenting immune signals, inhibiting immune escape of tumor cells, and regulating tumor microenvironment. This article summarizes the drug-carrying strategies (including membrane fusion, electroporation and genetic engineering, etc.), advantages and disadvantages of exosomes as drug delivery systems. It also discusses the factors affecting drug loading of exosomes, which provides some theoretical reference for applying them from the laboratory to clinical application.