After human society entered the modern era, not only the rapid socio-economic development and accumulation of social wealth, but also the emergence of new diseases, the treatment methods that are compatible with diseases are also changing. Immunotherapy is one of the great advances in the history of human medicine, and it has become the direction of treatment development to overcome malignant tumors. Immunotherapy is simply a concept of using the immune system to treat diseases, and immunotherapy can also be considered as using the immune system to treat diseases. The development of modern immunology has made people realize that the stability of immune function plays an important role in the occurrence, development, metastasis, reversal and regression of tumors. It can not only prevent the occurrence of cancer, but also may repel cancer cells even if they are already growing by strengthening the body’s immunity. Cancer treatment by strengthening the body’s immune system is the “immunotherapy” that is currently prevalent in the world. The principle of immunotherapy can be understood from the following aspects: 1. It uses biological cytokines that normal people rely on but tumor patients express less to mobilize the body’s own immune force to achieve anti-tumor effects, which has minimal side effects compared with radiotherapy and chemotherapy; 2, Treatment with molecularly targeted drugs has a clear target and has no effect on normal cells other than tumor cells, which can significantly curb the progression of tumor and prolong the life of patients with mid- to late-stage tumors that are not suitable for surgery. However, it should also be clear that although immunotherapy is good, it is not too mature to be the main method of treatment for the disease yet, and it still needs to be developed and improved to become a regular treatment modality. Immunotherapy can be used not only in the field of oncology, but should be seen in other fields as well.