Abstract: The major histocompatibility complex plays a crucial role in the immune response process, which is closely related to the occurrence and development of tumors and organ transplantation. Cellular immunity occupies an important position in tumor immunity and organ transplantation immunity, while humoral immunity also plays a significant role in organ transplantation immunity. Organ transplantation requires the induction and maintenance of immune tolerance, while tumors develop immune escape phenomena during their progression. In-depth exploration and comparison of the mechanisms of tumor immune escape and organ transplantation immune tolerance are of great significance for formulating reasonable immune tolerance induction strategies, improving the quality of life and prolonging the survival time of organ transplant patients.